122 AMI'MirODA NOIOIAT.TA. 



of tlie.sccond segment of the pleon waved. Eyes round, prominent. 

 Specimen imperfect. 



Huh. lilagnesian limestone, Durliani (Kirkbt/) ; Zechstcin-dolo- 

 mite, (Jliick.sbninn (Schlotheini). 



33. IS^A. 



Isfea, Ikhcards, Ann. des Sc. N((t. xx. p. 380 ; Hid. des Crust, iii. p. 26, 

 Eyes two. Superior antennte appendicnlate. Gnathopoda snb- 

 chelatc. Pereiopoda subchelatc. Coxa) of tlie third pair of 

 pereiopoda bilobed ; the anteiior lobe as deep as the preceding- 

 coxae. Posterior pair- of pleopoda bii'amons. TeLson single. 



Dana has formed a subfamily Is.T;Ai<r.B, based upon the prehensile 

 character of the pereiopoda, to reiceive Iscea and Anisojnis. I 

 have thought it desirable not to follow this arrangement, because 

 tile prehensile character is not dependent upon any fundamental 

 alteration of the organs. In Iscsa the pereiopoda have the propodos 

 on the flexible side developed into a palm ; but the whole of the 

 organs remain otherwise unaltered. Many species of Ajiphipoda 

 have the pereiopoda more or less prehensile. Some have a powerful 

 dactylos that impinges against the propodos, as Danvlnia ; others 

 have the propodos armed with short strong spines that antagonize 

 with the dactylos, as in Li/slanassa Cosfce ; but these, though pre- 

 hensile, bear no resemblance to the chela) proper of Crustacea. In 

 the present genus {Iscea) I think it is a peculiar habitat that has 

 induced an extreme of normal development. 



1. Isffia Montagui. (Plate XXII. fig. 1.) B.M. 



Isfea Montagui, Eduanh, Ann.' des Sc. Nat. xx. p. 380 ; Hifst. des 

 Crust, iii. p. 26. pi. '29. f. 11. 



Spence Bate, Brit. Assoc. Report, 1855; Synopsis, Sfc, Ann. Nat. 



Hist. Feb. 1857. 

 JMtite, Hist. Brit. Crust, p. 179. 



Eyes reniform. Superior antenna) half as long as the body; the 

 flagellum as long as the peduncle. Inferior antcnnse nearly as 

 long as the siiperior ; flagellum not longer than the last joint of 

 the peduncle. Coxa3 of the gnathopoda and the two anterior 

 pereiopoda gradually increasmg in depth ; of the thi-ee posterior 

 pereiopoda as gi'aduaUy decreasing. Gnathopoda similar in form ; 

 the second much larger than the fii-st, having the propodos ovate ; 

 pahn oblique, waved, defined by two small haii-s or spines. The 

 two anterior pairs of pereiopoda having the propodos dilated 

 posteriorly ; the distal extremity, against which the dactylos im- 

 pinges, slightly oblique, serrated. Three jiosterior pairs similarly 

 formed, but the propodos dilated anteriorly. Three posterior pairs 



