156 CALIFORNIA ACADEMY OF SCIENCES. 



side; carpus long, the inner and outer margins spiny, and the convex 

 upper surface armed with two rows of short spines; outer face more or 

 less flattened; lower side bulging and armed with a few short spines; 

 hand long, narrow, dorso-ventrally flattened, and bent inward at a slight 

 angle to the carpus; the rounded upper surface furnished with small, sub- 

 serially arranged granules which become more prominent on the fingers; 

 inner and outer margins sharp, granulo-denticulate and parallel; lower 

 surface of the palm with a broad, shallow concavity which extends nearly 

 to the dactyl. Left cheliped slender; merus spiny below; carpus subcy- 

 lindrical, with three rows of spines on the upper surface; hand narrow, 

 much longer than the carpus; palm very short; fingers long, narrow, and 

 curved downwards. Ambulatory. legs long, compressed, and very slender; 

 dactyls exceedingly long and slender and armed below with numerous 

 spines. 



Described from a single female specimen obtained 

 from the U. S. National Museum from Mr. Benedict, 

 who pointed out that it was not a true Pagurus but 

 belonged among the trichobranchiate forms. 



Northern California, Nitkasund, Kadiak Is., Atcha, 

 Kamtschatka (Brandt); Ion. 33 U 55' 30" N.; lat. 119 

 53' 30" W.; 19 fathoms! 



This species affords one of those curious cases of com- 

 mensalism with colonies of hydroids sometimes found 

 among deep sea pagurids.. The colony of hydroids cov- 

 ering the shell in which the crab lives forms a mem- 

 branous growth which extends beyond the boundary of 

 the shell and, in course of time, according to Mr. Bene- 

 dict, causes the shell to disappear, leaving its inhabitant 

 with a membranous, instead of a calcareous domicile. 

 In the specimen which I have, the covering is partly 

 formed by the tip of a broken shell, but mainly by an 

 extension of the membranous growth formed by the 

 colony of hydroids. This arrangement certainly affords 

 the crab the advantage of allowing it to grow, without 

 its having to undergo the troublesome experience of 

 changing its lodgings. 



