470 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL.21 



for the greater part of its length and could not be withdrawn without 

 dissection. It is difficult to see how the crab could exsert it in life because 

 of the rigidity of the member and its short basal attachment. 



Galapagos Islands specimens are quite broad, length to width ratios 

 in males being 1:1.54, in females from 1:1.56 to 1:1.60. In contrast, 

 the male of typical Aethra scruposa figured by Sakai (1938, pi. 40, fig. 

 3) is narrow, having a ratio of only 1 :1.50. In this it agrees with the 

 female figured by A. Milne Edwards, on the strength of which specimen 

 that author reduced Smith's A. scutata to subspecific rank. The male 

 holotype of A. scutata, however, has a length-width ratio of 1 :1.60, and 

 is therefore as broad as any of the Galapagos specimens. The ultimate 

 decision as to one species or two should be based on pleopod studies. 



Genus CRYPTOPODIA Milne Edwards 



Cryptopodia Milne Edwards, 1834, p. 360. Alcock, 1895, p. 281. Rath- 

 bun, 1925, p. 553. 



Type: The Indo-Pacific Cancer fornicatus Fabricius, 1787, by 

 monotypy. 



Description: Carapace very broadly triangular, with very large lat- 

 eral clypeiform vaulted expansions completely concealing the ambulatory 

 legs, and prolonged posteriorly far beyond the base of the abdomen; a 

 large space between the gastric and the cardiac regions triangular and 

 concave. Rostrum nearly horizontal, spatuliform, and very prominent. 

 Pterygostomian regions smooth, not ridged. Orbits very small, nearly 

 circular, with a suture in the superior margin. Epistome well developed ; 

 antennulary fossae narrow and somewhat oblique. Eyes very small and 

 retractile. Basal antennal [article] slightly dilated and not nearly reach- 

 ing the internal orbital hiatus, this hiatus filled by the second [article]. 

 Buccal cavity and external maxillipeds small. Ischium of the external 

 maxillipeds not produced at its anterointernal angle ; merus distally trun- 

 cated, with the anteroexternal angle slightly produced, the interior mar- 

 gin notched below the anterointernal angle. 



Chelipeds nearly as in [Parthenope] ; merus having a winglike lobe 

 on the posterior margin near to the distal extremity; palms of the cheli- 

 ped elongated, tricarinated, and dentated (as in [Parthenope ] ) ; fingers 

 short. Ambulatory legs slender, decreasing successively but slightly in 

 length, and having the fourth, fifth, and sixth [segments] more or less 

 distinctly carinated ; dactyli nearly straight. 



