416 EEPOET OF COMMISSIONER OF FISH AND FISHERIES. 



have been established, without description, in 1829. In the Precis 

 d'Entomologie, by the same authors, is a figure (pi. xxix, fig. 1), appa- 

 rently the same as that in the E^sume, which is there called Tanais de 

 Costa. Latreille,* in 1831, characterized the genus, basing it upon Gam- 

 marus Bulongii And., figured by Savigny. Westwood,t in 1832, proposed 

 for the same species the name Anisocheirus, without, however, mention- 

 ing any characters. In 1836, Terapleton | described and figured, with 

 evident care and accuracy, a species of this family under the name 

 Zeuxo Westwoodiana. This species has, according to his figure, six 

 segments in the pleon. Edwards, in his general work, Histoire natu- 

 relle des Crustac6s, figures and describes Tanais Gavolinii (tome iii, 

 p. 141, pi. 31, fig. 6), and refers the figure in the Precis d'Entomologie 

 to that species. In 1843, E.athke § described and figured Crossurus vit- 

 tatus as a new genus and species allied to Apaeudes and Tanais, but 

 there do not seem to be any characters of importance to separate it 

 from T. Gavolinii Edw., and, indeed. Bate and Westwood are inclined 

 to regard them as identical species. If, however, T. Bulongii be re- 

 garded as the type of the genus, there appears to be nothing but the 

 clothing of the basal segments of the pleon to separate the two genera, 

 and this character seems of no more than specific value, since T. Bu- 

 longii is described by Bate and Westwood as possessing the peculiar 

 "branchial appendages" at the base of the fifth pair of legs. These ap- 

 pendages are doubtless incubatory sacs, similar to those of T. vittatus. 



For the second genus I have hitherto used the name Paratanais Dana, 

 on the ground that Lepiochelia of the same author, although having 

 priority, was founded upon the characteristics of the male sex. The 

 type-species, however, of this genus, L. minuta, possesses all the charac- 

 ters of Paratanais that could occur in the male. Leptochelia Udwardsii 

 Dana, Tanais Edwardsii Kxoyer, moreover, belongs to the same genus, 

 and I have adopted the name for both sexes. 



The minute species, by which this family is represented on our coast, 

 may be readily recognized by the proportionately large and strong chelate 

 first pair of legs articulated to the united head and first thoracic segment. 

 The two genera are distinguished by the number of segments in the 

 pleon, which are five, with three pairs of pleopods in Tanais (p. 122), and 

 six, with five pairs of pleopods in Leptochelia (p. 126). 



Tanais Audouin and Edwards. 



Tanais Audouin and Edwards, '' R6sum6 (not Precis) d'Ent., p. 182 (without de- 

 scription, 1829), pi. xxix, fig. 1" (B. & W.) ; Precis d'Entomol., p. 46, pi. 

 xxix, fig. 1. 

 Edwards, Hist. nat. des Crust., torn, iii, p. 141, 1840. 

 Crossurus Rathke, Fauna Norwegens, p. 35, 1843. 



AntennuloB and antennse simple ; mandibles without palpi ; i)leon com- 

 posed of five segments bearing three pairs of ciliated pleopods below. 



* Cours d'Ent., p. 403. t Ann. Sci. nat., tome xxvii, p. .330, 1832. 



I Trans. Ent. Soc, vol. ii, p. 203, 1836. § Fauna Norwegens, p. 35. 



