CHAP. IV.] 



THE VOYAGE HOME. 



199 



length and 40 mm. in width ; the height of the shell in the fe- 

 male is 25 mm., in the male it is considerably less. The apex 

 is nearly in the centre of the dorsal surface ; the genital open- 

 ings are three in number, in the female very large ; the bilabi- 

 ate mouth is placed well forward on the ventral asj)ect ; and 

 the excretory opening is posterior and supramarginal. The 

 odd anterior ambulacrum is shallow, and tlie tube-feet which 

 are projected from it are large and capitate. The anterior 

 paired ambulacra are somewhat longer than the posterior. The 

 whole of the surface of the test is covered with a close pile of 

 small spines of a dark-green color; those fringing the ambu- 



FiG. 43. — Hemiaster Philippii, Gray. Accessible Buy, Kergueleu Island. Twice the natur.Tl 



lacral grooves are long and slightly curved, and they bend and 

 interdigitate so accurately over the ambulacra that one might 

 easily overlook the grooves at a first glance. The peripetalous 

 fasciole is somewhat irregular ; but in those examples in which 

 it is best defined, it forms a wide arch, extending backward on 

 each side a little beyond the lateral ambulacra of the trivium, 



