130 



SCIENCE. 



[Vol. I., No. 5. 



The base united with the olivine or enstatite 

 gives the structures which have been talien 

 bj' Drs. Hahu and AA'"einland as of organic 

 origin. I should expect to find the chondritic 

 structure in terrestrial peridotites, if anj- can 

 be found in which the cr3-stallization had been 

 arrested and subsequent alteration has not 

 taken place. 



The difference in structure between the rap- 

 \6.\y solidified, or chondritic, and the crystal- 

 line peridotites is not any greater than that 

 between the tachylitic, basaltic, doleritic, or 

 diabasic state of the basalts. 



All serpentines not veinstones, which have 

 been carefully studied, appear to belong to 

 peridotite, as a variety produced hy altera- 

 tion. 



4. Basalt. — -To the basalts I should assign 

 such meteorites as those of Jonzac, Stannern, 

 Constantinople, Petersburg, Juvenas, Sher- 

 gottj', Charkow, Frankfort, Shalka, Massing, 

 Busti, Manegaum, Ibbenbiiren, etc., so far as 

 their characters are at present known. These 

 have a lower specific gravitj" than the preced- 

 ing, a higher percentage of silica, less iron 

 and magnesia, but more lime, and usually more 

 aluminia. 



Some of these meteorites, like the Shergotty 

 and Manegaum ones, are apparently allied to 

 the gabbro varietj'' of basalt. 



Beyond the basalts are a few imperfectly 

 investigated forms, which, in the majority of 

 cases, are regarded as doubtful meteorites, 

 which appear to belong to the trachytes and 

 rh3-olites, but which require to be studied mi- 

 croscopicallj' before definite statements can be 

 made. Of these forms are some described bj' 

 Shepard, Silliman, and Grewingk. The car- 

 bonaceons meteorites have been too little stud- 

 ied to be given a definite position yet ; but, 

 excepting the carbonaceous matter, the}' chemi- 

 cally^ appear to belong to the peridotites, al- 

 though it is not improbable that they belong- 

 to a distinct species. 



So far as studied, I would class the meteor- 

 ites, the original and eruptive rocks, under the 

 following species : 1°, siderolite ; 2°, pallasite ; 

 3°, peridotite ; 4°, basalt ; 5°, andesite ; 6°, 

 trachyte ; 7°, rhyolite ; 8°, jaspilite. 



If further studj- shows that other species are 

 needed, then the signification of any of the 

 groups from which the new species are taken 

 can easily be naiTOwed. As manj- varietal 

 names can be employed under each species as 

 the needs of the science may demand ; but 

 they should be as few as possible, and should 

 hold the same relation to the species that the 



varietal names of quartz hold to the minera- 

 logical species quartz. 



This classification is intended to indicate 

 the probable arrangement of materials in the 

 earth from the interior outwards, beneath 

 the sedimentary formations, as well as to con- 

 nect, as far as possible, the sedimentarj' rocks 

 with those from which they were derived. 



Meteorites show, to ray mind, characters in- 

 dicating that they have been derived from a 

 hot, liquid mass, and not from an}^ gaseous or 

 solid body, so far as concerns the portion they 

 come from. Of all suggested sources, the 

 most probable one is the sun, provided the 

 eruptive activity- now observed on his surface 

 is sufficient to hurl such materials into space ; 

 if not now, in past times, when such action 

 was more powerful ; or else bodies of similar 

 nature. Meteorites, as far as I have studied 

 them, show no fragmental or tufaceous charac- 

 ter beyond such as would be formed by hot, 

 plastic drops falling into a liquid mass of the 

 same material. 



Thej' also show that they have not been 

 formed in a locality where life could have ex- 

 isted ; for, in that case, the readilj^ alterable 

 materials of which t\\&y were composed would 

 have suffered change. M. E. Wadsvforth. 



MOLLUSKS OF THE FAMILY 

 COCCULINIDAE. 



Examination of specimens of a Cocculina or 

 an allied genus of that familj-, from the north 

 Atlantic, shows some remarkable features. 

 These moUusks, recentl}' discovered by the 

 U. S. fish-commission in the deep sea, are most 

 nearly related to the kej-hole limpets (Fissurel- 

 lidae). The specimens obtained by Prof. Ver- 

 rill, and examined by me, were, however, all 

 females. A number of specimens, of another 

 species, sent me by Dr. Jeffreys for examina- 

 tion, contained individuals of both sexes ; and 

 the males wei'e found to possess a verge, per- 

 manently exserted from the inner side of the 

 right tentacle. This is a feature hitherto en- 

 tirelj' unknown in the order to which the}^ be- 

 long, none of the littoral forms of anj- of the 

 families possessing anj' such organ ; though, 

 like other limpets, dioecious. It is of course 

 probable that the species of Cocculina found 

 by the fish-commission and Prof. A. Agassiz 

 agree in this character with the form from the 

 north 7\.tlantic, about to be described by Dr. 

 Jeffreys ; but the latter shows other differences 

 which may require it to be subgenericallj' sepa- 

 rated from Cocculina proper, though evidently 

 a member of the same family-. Wm. H. Dall. 



