The properly oceanic genera include all the Calanidæ, excepting Diaptomus and Notodelphys; all the Corycaida; with only the single genus Setella among the Cyclopida.

Among the Calanidæ, the genera are mainly tropical, yet each affords some extra-tropical species; and those which are most abundant in the colder waters are Calani or closely allied. Setella occurs beyond the tropics; but all the species thus far examined are found in the Torrid zone. Pontella is more of a warm-water genus than Calanus. The Corycæidæ are to a large extent tropical; the genus Corycæus is almost exclusively so, while Sapphirina is common in the Temperate zone. The Steropinæ are Frigid species.

Although the Calanidæ are more varied in species within the tropics, they abound more in individuals in the colder seas. Vast areas of "bloody" waters were observed by us off the coast of Chili, south of Valparaiso (latitude 42° south, longitude 78° 45′ west, and latitude 36° south, longitude 74° west), which were mainly due to a species of this group; and another species was equally abundant in the North Pacific, 32° north, 173 west.* They have been reported as swarming in other seas, constituting

*The species in the former case was the Pontella (subgen. Calanopia) brachiata; and in the latter, Calanus sanguineus.

the food in part of certain species of whale. Such immense shoals we did not meet with, within the tropics.

Among the Daphnioidea, the genera Daphnella, Penilia, Ceriodaphnia, and Lynceus were observed by us in the Torrid zone. Of the Cyproids, Cypridinia, Conchocia, and Halocypris are oceanic forms, and mainly of the tropical oceans.

The Caligoids spread over both, zones. Caligus and Lepeophtheirus reach from the equator to the frigid seas; Nogagus, Pandarus, and Dinematura are represented in both the Torrid and Temperate zones.

GENERAL REMARKS AND RECAPITULATION.

We continue by presenting a few general deductions from the tables, and a recapitulation of some principles.

A survey of all the great divisions of Crustacea, shows us that exclusive of the Entomostraca, they are distributed, according to present knowledge, as follows:

Taking the sum of the Frigid and Temperate zone species (subtracting the fourteen common to the two) we have 1036 species in the torrid regions to 1069 in the extra-torrid, seventy-five of which are common to the two. This shows a nearly equal distribution between the zones. But excluding the Brachyura, the numbers become 501 to 811, giving a preponderance of more than one-half to the Temperate zone.*

* Adding to the numbers above, the species which have been necessarily left out as of uncertain locality, amounting to one hundred and forty in all, and inserting also the Entomostraca, it makes the total of described living species in 1853, as follows:

Brachyura,

Anomoura,

Macroura,

Anomobranchiata, (Mysidea, Squilloidea, Amphionidea,)

Isopoda,

Anisopoda,

Amphipoda,

Entomostraca,

Total,

830

262

297

-1389

115

295

57

341

693

492

2689

The number of species collected in the cruise of the Expedition (exclusive of those lost in the wreck of the Peacock, which included nearly all the collections of

The species of highest rank among the Brachyura, Macroura, Isopoda, and Amphipoda, the four principal types in the above, belong to the extra-torrid zones; and in subordinate groups or families, it is often true that the genera of superior grade are extra-torrid, in contrast with the others which are torrid genera. Higher groups, characteristic of the colder regions, sometimes show degradation among those species of the group that are tropical; and the tropical sections also may continue the line of degradation by an extension again into the colder seas.

As we descend in the scale of Crustacea from the Podophthalmia to the Tetradecapoda, the number of cold-water species increases, becoming in the latter group, three times greater than the warm-water species. It is an important fact, nevertheless, that this increase of cold-water species is still no mark of degradation; the particular facts that have been discussed, leading to a very different conclusion. Other principles follow.

These are

First, that the two types, the Decapodan and Tetradecapodan, are distinct types, to be independently considered, and not parts of a series or chain of species-a fact illustrated in the chapter on the Classification of Crustacea.

Second, that the preponderance of cold-water species is the reverse of what must have been true in the earlier geological epochs, when the oceans had a somewhat higher temperature; or were to a large extent tropical.

Third, that the progress of creation as regards Crustacea, has ended not where it begun, in multiplying the species of warmer waters and giving them there their superior developments, but in carrying species to a higher perfection in the colder regions of the oceans. A preponderance of species in the warmer seas is perhaps to be expected, since warm waters have prevailed even more largely than now in earlier epochs. But it would seem, that the introduction of the higher grades of Crustacea required, not merely the cooler waters of the present tropics, but even the still colder temperature of the Temperate zone, and therefore the present condition of the globe.

two seasons in the tropical regions of the Pacific) is nearly 900; and the number of new species described is 658, distributed among the groups as follows:

The genera of Fossil species commence with the Entomostracans and Trilobites in the Palæozoic rocks. Next appear certain Thalassinidea and Astacoid species, in the Permian system; then Mysidea, Penæidea, many Thalassinidea, Astacoidea, and Anomoura, in the Oolitic system; then a few Cancroids and Leucosoids in the Cretaceous, which become much more numerous in the Tertiary system, along with some Grapsoids. None of the Maioids, the highest of Crustacea, have yet been reported from either of the Geological epochs.

The number of individuals and the size are, for the Brachyura, greater in the Torrid zone than in the colder regions. But for the Macroura, the species of cold-water genera average nearly twice the lineal dimensions of those of warm waters; and the number of individuals also may possibly be greater.

In stating the conclusion respecting the Macroura, on a preceding page (last volume, p. 325), we omitted to give in detail the mean sizes of the different groups. The following are the results, including the Galatheidea which are closely related to the Ma

The table shows that the torrid species, in none of the groups, average larger than the extra-torrid. The cold-water Palinurida are as large as the largest warm-water species, and will outweigh them; the cold-water Galatheidea, are ten times the average length of the warm-water; the Alpheinæ, Palamoninæ, and Penæidæ are at least as large in the temperate regions as in the torrrd. There is hence nothing in the tropics to balance the Astacidæ, a group of large species, some of them gigantic; nor the Crangonidæ, nor Pandalinæ. The genus Palæmon, in the Torrid zone, averages larger than in the Temperate, the ratio being 3.5 to 2.4; the former amount being reduced to 2-3 for the Palæmonina, by the species of the other tropical genera, which are mostly quite small. Yet, taking the ratio of 3:5 to 2-4, it affects but little the balance against the Torrid zone.

As to bulk, also, the Temperate zone probably has the preponderance; yet our data are less definite. In the Galatheidea, the cold-water species are not only ten times larger lineally (which implies at least eight hundred times cubically), but they are far more prolific, swarming in vast numbers where they occur. The Thalassinidea are more numerous in extra-torrid species than torrid, as well as larger in size. The Scyllaridæ are mainly tropical; but the species are not of common occurrence, compared with the Astacidæ, which abound everywhere, and these, as well as the Crangonidæ and Pandalinæ, are all Temperate zone speThe Palæmoninæ and Penæidæ probably preponderate in the tropics, and this may be also true of the Alpheinæ. Taking a general view of the whole, and considering the fact, that the extra-torrid species rather outnumber the torrid, we believe that the deduction above stated is correct.

In the Tetradecapoda, the number of species, the number and diversity of genera, the number of individuals, and the bulk, are all greater in the extra-torrid seas than in the torrid, as has been explained on a preceding page; and this is especially true of the Amphipoda.

The tendency to spinose forms among the species of the colder temperate regions, or Frigid zone, has been remarked upon on page 9, as exemplified among the Gammaridea, the Crangonidæ, Lithodes, and Maioids.

(To be continued.)

ART. III. Contributions to Mineralogy; by Dr. F. A. GENTH of Philadelphia.

(Continued from vol. xviii, p. 410.)

5. Tetradymite.

AFTER making the examination of the Tetradymite from Davidson county, N. C. (Am. Journ., 2d Ser., vol. xvii, page 81), I was very desirous to reexamine the mineral, which had been analyzed by Mr. Coleman Fisher, Jr., (Am. Jour., 2d Ser., vol. vii, p. 282). Fortunately Prof. R. S. McCulloh (who was at the time of its discovery at Commodore Stockton's mines in Virginia, Melter and Refiner at the U. S. Mint) had preserved some of the same material, which was analyzed by Mr. Fisher, and he very kindly gave me all that he had for examination. This was sufficient for the whole investigation. The pieces were of two different kinds, viz: Tetradymite associated with quartz and gold, and Tetradymite in broad folia, sometimes one inch in diameter, implanted in a decomposed micaceous slate. The latter mineral undoubtedly came from the Tellurium Mine, Fluvanna county, Va. and is that analyzed by Mr. Fisher; the former is