14 PIM*. KKi'our OK ri:<)(;i{Kss. c. k. hkeciikr. 



outwards and backwards over the anterior end, extending 

 in a broad oiirve along the lower margin, rapidly recurving 

 around tlie lower posterior portion, and continuing concave 

 an<l oliliquely forward to the extremity of the hinge, mak- 

 ing rhe hinge-line appear as slightly produced. 



The cephalic area occupies the anterior third of the valves, 

 and is marked at its base by two broad flattened oval eleva- 

 tions, of which the lower one is somewhat the larger. Optic 

 node prominent, situated above the middle of the area. 



Thoracic region convex over the anterior portion, becom- 

 ing flattened on the posterior half, without nodes or ridges. 



Abdomex having a length of less than half that of the 

 valves, composed of two naked cylindrical segments. The 

 posterior segment is one-third longer than wide, somewhat 

 larger at its anterior end. Anterior segment partially con- 

 cealed by the carapace in the specimen described. The 

 margins are slightly thickened. 



Telsox consisting of a stout triangular spine flattened on 

 the ventral side, rounded above, and marked by a longitud- 

 inal carina along the middle. Lateral spines longer than 

 the extension of the telson, flattened; margins thickened ; 

 marked by two sharp longitudinal ridges on the dorsal face. 

 The inner edges of the movable spines are crenulate for the 

 attachment of setse. 



Test thin, not exceeding xV i^mi. in thickness, minutely 

 wrinkled over the surface of the valves, except on their 

 margins and the abdominal segments which are ornamented 

 witli flne curving striae or vascular markings. 



An entire left valve has a greatest length of 23 mm., 

 width 10 mm., and hinge-line 20 ram. In a specimen 

 preserving a portion of the valves with the abdomen and 

 its appendages, the valves have a width of 11 mm., and 

 the length from the distal extremity of the telson to the 

 insertion of the abdomen with the carajjace measures 20 

 mm. 



The three specimens of this species observed, present 

 such marked differences from any described form, that it 

 seems advisable to arrange them under a new generic desig- 

 nation. The presence of crenulations along the inner mar- 



