Zoology. 135 



to 2000 miles, with a breadth or depth of 20 miles, peaks above 5 miles 

 high, distributed throughout its whole extent, and passes similarly ex- 

 tended, yet seldom or never falling below 15,000 feet; and all this 

 though we admit Humboldt's somewhat theoretic negation of the gene- 

 ral opinion, that Hemachal, and not, as he contends, Kuenlun, is the 

 chain which divides Asia from end to end ! 



III. Zoology. 



1. Synopsis of the Genera of Gammaracea ; by James D. Dana. 

 The tribe of Amphipoda among Crustacea includes the subtribes Gam- 

 maracea and Hyperiacea. The former of these subtribes consists of 

 six groups or families. 



Fam. 1. Orchestid^e. Saltatorise. Palpus mandibulars obsoletus. 

 Corpus compressum, epimeris latis. Styli caudales duo postici breviores. 



Fam. 2. Gammarid.e. Saltatorise vel natatorias. Mandibular palpi- 

 gerae. Corpus saepius compressum. Antennae flagello confectse, non 

 pediformes. Styli caudales duo postici sive longi sive breves. 



Fam. 3. CorophiDjE. Gressorise. Corpus plus minusve depressum, 

 hneare, abdomine recto, normali, epimeris angustissimis vel obsoletis. 

 Mandibula palpigera. Antenna? pediformes. 



Fam. 4. Icilid^e. Corpus depressum, latum, abdomine normali, in- 

 nexo, pedibus late expansis instar Aranese. Antenna non pediformes. 



Fam. 5. Chelurid,e. Corpus vix compressum. Abdomen abnor- 

 mal, segmentis duobus tribusve coalitiset irregularibus ; stylis caudali- 

 bus sex, dissimilibus. Antennae breves pediformes. 



Fam. 6. DuucHiDiE. Isopodis affines. Corpus depressum, lineare. 

 Antennae pediformes. Abdomen abnormale, 5-articulatum, stylis duo- 

 bus. Antennae pediformes. Pedes tertii quartique breves, sex sequen- 

 tes elongati, Caprelliformes. 



synop>is, the synonvmv is included only so far as it is not con- 

 — - m Crustacea by Milne Edwards (Paris, tome hi, 1840); copious 

 notes also are added. The number of new genera introduced since 1840 is quite 

 Nge, and a few fire instituted from the collections by the writer in the Exploring 

 Expedition* 



tained 



add a word on a single point in the distinctions 

 among the Orchestkke and Gammaridae has often 



»f genera. The size of the 



)een deemed to some extent 



., a - D -«—. character. But it fc now *eD known that the gradations in 



the same group are imperceptible, and farther, females may have minute and hardly 

 Prehensile feet, while in males of the same species the corresponding hands are quit 

 W. On this ground, Fr. Midler has lately denied the propriety ot separating th 

 Orchestic and Talitri (Archiv fiir Naturg., 1848, p. 53). There is however a wide 

 difference between the species having a stvliform joint terminating the mom* pair 

 of 1' id those with a hand howler minute or obsolescent. The only fflde course 



a Pl>ears to the writer to consist in drawing the line between ***** hm*p a p^er 

 • dm however mall or large, closing upon the fifth joint, mA the* spm< • ^ 

 «» extend *<1 finger or claw not chmv<i' , Kroyer s Anmys, according to his descrip- 



volu 



The Crustacea of the Exploring Expedition under Captain V ilkes will form a 

 me of text in 4to. accompanied with figures of all the species ma folio atlas. 

 -™tf descriptions wfll from time to time appear in the Proceedings of the American 

 Academy of Arts and Sciences of Boston, part of which, relating to the Bofamoifam 

 ami ^eluding upwards of 150 species, has already been published. Ihe number of 

 new s I*cies of Amphipoda hi the collections exceeds eighty. 



