^TsoY'"] PROCEEDINGS OF THE NATIONAL MUSEUM. 655 



margin sinuous, its lobes visible from above (Fig'. 0). The external 

 orbital tooth and the next lateral tooth are flnely dentate; posterior to 

 the eervical suture there are ten small spiniform teeth lu^arly equal in 

 size, followed by a diminishing series of spinules on the posterolateral 

 margin; the first of the ten teeth has, on one side of the carapace, one, 

 on the other side two, accessory spinules. Orbital fissure broad, shal- 

 low, U-shaped. Inferior surface of the carapace granulate near the 

 lateral margin, and granulate and pubescent on the jugal area. Max- 

 illipeds broad, considerably overlapping the jugal area; ischium much 

 wider at the distal than at the proximal end ; merus more quadrate 

 than in preceding species. Last two segments of the nuile abdomen 

 longer and narrower than in lamcllifrons (Fig. 7); appendages of first 

 segment with superior i)ortion of the extremity armed with three un- 

 equal spines, the inferior portion having a concave oval area. Clieli- 

 peds unequal, punctate, with scaly granules, which form rugosities on 

 the outer surface of the merus; merus and carj)us armed similarly to 

 those of colomhianns, except that there is not a continuous line of 

 granules near the upper margin of the inner surface. Hands rough, 

 with scaly granules, especially on the margins. Large hand deep, 

 lower margin very convex. Fingers in contact. Meral joints of am- 

 bulatory legs compressed and widening toward the center; upper 

 margins of meral, carpal, and i)ropodal joints, and lower nuirgin of 

 propodal joints spiiiulous; dactyls very slender. 



Length, 32.5; Avidth without spines, 49; length of cheliped about 70'""'. 



Found on dry land near a small creek which fiows into the Escon- 

 dido Eiver, 50 miles from Bluefields, iSTicaragua, by Mr. Charles W. 

 Eichmond, October 30, 181)2; one male (17725). 



POTAMOCARCINUS. 



Established by Milne Edwards* for a species (P. arniatus) which 

 diflers from PscudothcJphnm in having the superior frontal crest sharp 

 and lamellate, and more prominent than- the inferior, the carapace 

 armed with strong spines and an external orbital hiatus. 



This geiuis is doubtfully distinct from PHeiKJothclphnsa, some species 

 of which have an orbital hiatus; in P. richmondi the front is sharp and 

 lamellate, though not entirely concealing the inferior crest. In Fscii- 

 (lothelphum can be seen every gradation between the sharp-crested 

 front and the smooth front without a ridge. There seems to be no ex- 

 ternal character to distinguish Fotamocarcinm except the strong mar- 

 ginal teeth, which is hardly a generic character. The following species 

 is therefore placed provisionally in this genus. 



*Aim. Sci. Nat. (3), xx, p. 208, 1853. 



