306 Verrill, Notes on Radiata. 



specimens were obtained at low-water. E. gihhosiis was originally 

 described from the Galapago Islands. 



The larger specimens have a test about 2 inches in diameter, and 

 1 in height ; spines "9 long ; diameter of actinal area '7 ; of abactinal 

 area, including genital plates, *6. 



The form is rather depressed, the abactinal area somewhat sunken, 

 the sides regularly arched, the lower surface nearly flat. The test 

 is rather thin. The actinal area is small, with slight cuts. The am- 

 bulacral zones are nearly as broad as the interambulacral, and slightly 

 elevated above them. The poriferous zones are broad, becoming a 

 little wider beneath ; the pores, arranged in oblique, slightly curved 

 rows of four or five pairs above, form on the lower surface more trans- 

 verse and nearly straight rows of four pairs, with rows of very small 

 tubercles intervening. The ambulacra have two rows of primary 

 tubercles, with an irregular median row of small tubercles between 

 them. The interambulacra have two primary rows of somewhat 

 larger tubercles, midway between the sides and median line, and 

 a row of smaller ones, on each side, bordering the poriferous zones, 

 and a median double row of alternating tubercles of still smaller 

 size. The genital plates are small, broader than long, uniting so as 

 to separate the small ocular plates from the anal area. Madreporic 

 plate small, transversely oval. Spines not very numei*ous, long 

 slender, with fine longitudinal striations, the ribs crossed by fine 

 lines. Color, in alcohol, dark purplish brown, when dry test often 

 variegated with light green and whitish ; spines dark green, often 

 tipped with purple. 



Nearly every specimen examined is irregular in the form of the 

 shell above, near the abactinal area, which is, also, generally distor- 

 ted or enlarged on one side, where the shell is thinner. This distor- 

 tion, which often amounts to gibbosity, is irregular and inconstant, 

 and is caused by a parasitic crustacean [Fahia Chilensis Dana) allied 

 to the Pinnotheres, which inhabit oysters and other bivalve mollusca. 

 This curious parasite* appears to force an entrance into the anal orifice 

 when quite small, and, having effected a permanent lodgment there, 

 causes a dilation and malformation of the intestine, which eventually 

 forms a large membranous cyst or sac, often in the larger specimens 

 extending from the summit to the lower side of the shell, along one 

 side, to which it is attached by fibrous tissues. In one instance the 

 cyst was an inch in length and nearly half an inch in diameter, en- 

 closing a female crab of corresponrling size, with large numbers of 

 eggs attached to its abdominal appendages. A large opening is 



* Pinnaxodes hirtipes Heller, appears to be the same species. 



