574 CALIFORNIA ACADEMY OF SCIENCES. 



hands oblong, compressed; lingers shorter than the pahn. 

 The hrst two pairs of ambulatory legs are slender (the 

 second somewhat larger than the first) and furnished with 

 slender, nearly straight tarsi which are about equal to the 

 propodal joints. The fourth pair of pereopods is very 

 large, considerably longer than the breadth of the carapax 

 and about two-thirds as wide as the carapax is long; on 

 the posterior margin of the meros is a kind of flange above 

 which is a shallow groove ; tarsus shorter than the pro- 

 podus, stout, curved. The last pair is small and propor- 

 tionately stouter than the anterior ambulator}- legs, and 

 has the edges densely hairy. This pair scarcely reaches 

 beyond the middle of the meros of the preceding pair; 

 the carpus and propodus are about as broad as long, the 

 tarsus short and stout, similar to that of the fourth pair. 

 All of the legs are compressed and more or less hairy. 

 Abdomen of female transversely elliptical and seven- 

 jointed. Abdomen of male seven- jointed, the first two 

 joints shorter than the others, the last joint broader than 

 long and rounded at the tip. The male abdomen tapers 

 evenly from the base which is about one -third the width 

 of the thoracic sternum to the last joint. 



This crab is remarkable for its grreat width and the 

 great development of the fourth pereopods. It lives in 

 tube of a species of annelid. 



Lockington in his description of this species states that 

 the third joint of the external maxillipeds is very small, 

 the second stout and large. He probably mistook the 

 meros for the second joint, for the latter is rudimentary 

 or absent in the subfamily to which Piniiixa belongs. 



Locality: Tomales Bay. 



This description is taken from Lockington's t^'^pe spec- 

 imens. 



