40 CALIFORNIA ACADEMY OF SCIENCES. 



Chioncecetes Tanneri Rath. 



Chionoecetes Tanneri Kathbun M., Proc. U. S. Nat. Mus., Vol. XVI, 1893, 

 p. 76, PL IV, figs. 1-4; and Vol. XXI, 1898, p. 573. Newcombe, Bull. 

 Nat. Hist. Soc. Brit. Col., 1893, p. 19. 



Carapace a little wider than long, with the postero-lateral angles broadly 

 rounded; branchial regions tumid and produced laterally, concealing the 

 lateral margins. The carapace is covered with spines, instead of wart-like 

 tubercles as in opilio, the most conspicuous of which are arranged in more 

 or less irregular rows. A nearly transverse row of tubercles on the 

 branchial regions, which, near the side of the carapace, curves around 

 and runs obliquely forwards towards the orbit. Posterior margin of the 

 carapace spinulous; above the outer portions of this margin there begins 

 another row of spinules, which is continued around the sides of the cara- 

 pace, the spines becoming smaller anteriorly; at the bend in the row of 

 spines on the branchial regions there begins another row of spines which 

 runs forward to the anterior portion of the buccal area, the spines becom- 

 ing smaller and more thickly set anteriorly, where they gradually spread 

 out into a small patch of minute, irregularly placed tubercles next to the 

 buccal area. An irregular row of spinules across the anterior portion of 

 the median area. The upper margins of the orbit and the outer sides of 

 the rostrum are spinulous. A small elevated patch of spinules on the 

 cardiac region, in front of which is a deep depression, separating the 

 branchial regions, which is rather narrow behind, but widens anteriorly, 

 and divides into two broad depressions extending either side of the 

 median area. Eostral horns upturned, narrower than in opilio, the notch 

 between them more prominent. Basal antennal joint spinulous below. 

 Maxillipeds more or less spinulous, and not reaching the anterior margin 

 of the buccal area. Chelipeds spinulous, small in the female; hand nar- 

 row; fingers long. Legs spiny, becoming smoother toward the tips. A 

 transverse spinulous or granulated ridge in front of the abdomen, in front 

 of which the sternum is excavated. First two or three joints of the 

 abdomen with a transverse spinulous or granulated ridge. 



The largest specimen in the series studied by Miss 

 Rathbun gave the following measurements: 



Length from base of rostral horns 119 mm. 



Width without spines 130 mm. 



Length of first ambulatory leg 316 mm. 



Length of merus of first ambulatory leg 134 mm. 



Miss Ratlibun's table of measurements of 18 specimens 

 shows that in the smaller specimens the length more 



