656 NEW SPECUvS OF ERESlI-WATi:il CKA15S RATHUUN. 



Potamocaiciiuis nicaraguensis. 



(i']. i,\x\i; I'l. i.xwii, I'iys. I-:{.) 



/'o/rt//i()(«m"H((.s <n-Hi«/i(.v Stiiii])8i)ii (nol Milin' lOdw iirds), I'roc. Ar.nl. \;it. Sri. riiilji. 

 \, p. 100, 1858. 



Stimpson, ill his unpublished report on the ('rnstacoa coHected by 

 tlie North Pacific l<]x[)l()rin,i;" Expedition, says of P. ^(rwa/?/.s, " We luive 

 bnt one specimen of this si)ecies, ii small male, half an iiicli in length. 

 Jt dirters somewhat from the large female described by Milne Edwards, 

 in that the carapace is punctated, and, toward the lateral margins, 

 somewhat granulated. The second and third antero-lateral teeth are 

 bilid. Dactyli scarcely qiiadrangnlar, almost rounded, also smaller 

 and less spinnlose. It was found at Omotepec Island in Lake Nica- 

 ragua, by Mr. Charles Wright, botanist of the expedition,"' 



Pofaiaocarcinus nicaraf/ucusis is a large species; snnill specimens 

 agree with Stimpson's diagnosis, except that the dactyls are not less 

 spinulous than in Milne Edwards's figure ofarniatus. 



('arai])ace broader anteriorly than in armatus, slightly convex, dis- 

 tinctly marked with small puncta'-, grainilate near the lateral margins, 

 the grannies most i)rominent in young specimeus. Cervical sidcns 

 deep and cuiAcd; there are wide and deep grooves either side of the 

 l)osterior gastric area, and small Y-shaped grooves between them. The 

 epigastric lobes are well marked, divided by a narrow sulcus leading 

 to the front. Superior frontal margin horizontal, gianulate, more 

 advanced in the central i)()rtion; nu'dian lissnre V-sliai)ed. Front 

 concaxe, the inferior margin much behind tlie su])erior, the two lialves 

 separately arched upward, Postorbital tooth obtuse, outer margin 

 rounded. Second tooth broadi'r, ot)tnse, often with one or more acces- 

 sory teeth on its margins. Third tooth, that directly posterior to the 

 cervical suture, broad, very variable in shape, hut always bilobed. 

 llemaining large teeth, four to six in number, irregular in shape and 

 ])osition, acute, spinous. Theic are often small intervening teeth. 

 Posterolateral margin M'ith sev«'ral spinules which decrease in size 

 from the lateral angle. External orbital hiatus deep and M-ide; orbital 

 margin granulate. Lower surface of the carapace grainilate near the 

 lateral margin and on thejugal area. The margin of the epistome is 

 three-spined; median spine long and curved upward. \s in arniata, 

 the endognath of the external maxillipeds is very wide and covers a 

 jiortion of the Jugal region; the exognath is much shorter than in 

 (n')nata^ never exceeding one-half the length of the ischium. The 

 .ippendages of the first segment of the male abdonuMi are \ery stout, 

 and at \\w summit present a concave outer surface Avhich has a s]>ine 

 at the antero inferior angle, a lobe at the antero-superior and jiostero- 

 inl'ciior angles, and two si)ines at the i)ostt'ro-superior angle (I'l, LXXVI? 



