1907.] CRUSTACEA OP THE THIRD TANGANYIKA EXPEDITION. 265 



Dimensions as follows : — 



Male (probably young specimen) : mm. 



Length of carapace 20'3 



Breadth of carapace 30-7 



Fronto-orbital width 19'7 



Width of front lO'l 



Adult female (largest specimen) : 



Length of carapace 33'7 



Breadth of carapace 48-2 



Fronto-orbital width 30-0 



Width of front 13-8 



liemarks.— This species comes into Miss Rathbiin's key nnder 

 the heading c', where the carapace extends laterally more than 

 an orbit's breadth beyond the external orbital angle. It finds its 

 place in the same subdivision (cj) as the species amhiguus and 

 mrogoroensis, and that portion of the key, modified to include it, 

 is accordingly given below : — 



g'. Anterior branch of cervical suture absent. 



h. Ischium of external maxillipeds without longitudinal furrow. 



j. Anterior portion of female sternum hairy pla tynotus. 



f. Anterior portion of female sternum not hairy mrogoroensis *. 



h'. Ischium of external maxillipeds with longitudinal furrow ... a mbiguns. 



The principal points in which jjlati/notm differs from ambiguus 

 on the one hand and suprasulcatus on the other are also given m 

 tabular form. The most striking features of the new species are 



stiprasulcatus Hilg. 



platgnotus, sp. n. 



ambigims Rathbun. 



Carapace moderately vaulted. ' Carapace much flattened. Carapace distinctly vaulted 



Antero-lateral margins granu- 

 lated. 



Anterior branch of cervical 

 suture present. 



Fronto-orbital width "60 that 

 of carapace. 



Ischium of external maxilli- 

 peds without longitudinal 

 furrow. 



Fingers pointed and slightly 

 hooked. 



Antero-lateral margins ! Antero-lateral margins 

 denticulated. ' granulated. 



Anterior branch of cer- 

 vical suture absent. 



Anterior branch of cervi- 

 cal suture absent. 



Fronto-orbital width -62 Fronto-orbital width -57 

 that of carapace. that of carapace. 



Ischium of external 

 maxillipeds without 

 longitudinal furrow. 



■ Fingers distally hol- 

 lowed out spoon-shape 



Ischium of external maxil- 

 lipeds with longitudinal 

 furrow. 



Fingers pointed and 

 slightly hooked. 



the flattened carapace, the denticulated antero-lateral margin, and 

 the character of the fingers. 



* It is by no means obvious whv Miss Rathbun has inserted the form mrogoro- 

 ensis here, under the heading c' , when it is quite clear from Hilgendori s description. 



