NO. 1222. ISOPODS OF THE ATLANTIC COAST— RICHARDSON. 537 



of the. abdomon i.s markod ])v a .sinus, which is ahiiost coniplotely filled 

 }\y a sino-le lai-g'e tooth, which is posteriorly triano-ular and extends 

 ])eyond the lati^-al teeth formed by the sinu.s. This cen- 

 tral tooth Ix^ars a small, pointed tubercle near its base. 

 The uropoda are .sli*>-htly incurved, and are somewhat 

 longer than the abdomen, 

 Fi«.2o.— ABDo- The color is a dull yellow. 

 MEN OF ciLi- -pi^g lower pai"t of each thoracic segment is densely 



CMA. LINGUI- 1 11 11 •' i> 1 ' 



c.\uDA. granulated, as well as the whole surface of the abdo- 



men. The edges of the segments and the uropoda are 

 fringed with hairs. 



Ilahltat. — C'ape Catoche, Yucatan. 

 Type.— Ciit. No. 23908, U.S.N.M. 



40. N^^SA Leach. 



It is not probable that the two following: species belong to the 

 genus Najsa, but being unable from lack of specimens and from the 

 character of the description to determine where they do belong, I have 

 retained them for the present with Naisa where Say placed them, 



96. NiESA DEPRESSA Say. 

 Nn^m depremt Say, Jour. Ac. Nat. Sci. Phila., I, 1818, pp. 483, 484. 

 IlaVdat. — Egg Harbor, New Jersey. 

 Depth. — Found on surface. 



97. N/ESA OVALIS Say. 



At&so oralis Say, Jour. Ac. Nat. Sci. Phila., I, 1818, pp. 484, 485. 



Ilahitat. — St. Johns River, Florida. 

 Depth. — Found on surface. 



III. VALVIFERA or IDOTEOIDEA. 



ANALYTICAL KEY TO THE FAMILIES OF VALVIFERA. 



a. Body more or less l)road, depressed. Legs usually nearly alike, but first three 

 pairs sometimes with propodus dilated and dactylus reflexed. 



Family XII. Idoteid/E (p. 537). 



a'. Body narrow, scarcely depressed. Four anterior pairs of legs unlike three pos- 

 terior pairs, and not ambulatory, nor strictly prehensile, directed forward, 

 slender, ciliated, with terminal joint minute; last three pairs stouter, ambula- 

 tory, with terminal joint bifid Family XIII. Arcturid^ (p. 545). 



Family XII. IDOTEID^. 



ANALYTICAL KEY TO THE GENERA OF IDOTEID.E. 



a. Sides of head emarginate or cleft and laterally produced beyond eyes, which are 

 situated upon its dorsal surlace Three anterior pairs of legs, with penul- 

 timate joint or propodus dilated, and forming, with retlexible dactylus, a 

 prehensile hand. All the epimera from the second to seventh segments 

 distinctly defined 41. Chiridotea. 



