GYMNOPATAGUS MICROPETALUS. 227 



Key to the Species of Gymnopatagus. 



No large primary tubercles in interambulacrum 5 abactinally. 



Ambulacrum III more or less depressed at ambitus; petals well formed and .vide; 

 not more than 15 big primary tubercles in each of interambulacra 1 and 4 



abactinally valdiviae. 



Ambulacrum III not at all depressed. 



Test widest across posterior petals, which are a little curved; no big primary 



tubercles in interambulacra 2 and 3 abactinally micropelalus. 



Test widest just back of apical system; posterior petals straight; big pri- 

 mary tubercles conspicuous in interambulacra 2 and 3 abactinally . . pulchellus. 

 Large primary tubercles present in interambulacrum 5 abactinally. 



Ambulacrum III markedly depressed at ambitus; test highest anterior to apical 

 system; numerous big primary tubercles in interambulacrum 5 within the 



peripetalous fasciole magnus. 



Ambulacrum III very little depressed at ambitus; test highest posterior to 



apical system; few (5-10) big tubercles in interambulacrum 5 abactinally . obscurua. 



Gymnopatagus valdiviae. 



Doderlein, 1901. Zool. Anz., 24, p. 23. 



This species was taken by the Valdivia in 412-757 fms. off the coast of 

 Somaliland, East Africa. 



Gymnopatagus micropetalus, 1 sp. nov. 

 Plates 146, fig. 14; 154, figs. 4-6; 158, fig. 5. 



Length 45 mm.; width across anterior petals, 33 mm.; width across pos- 

 terior petals, 38 mm. ; height back of apical system, 20 mm. The shape of the 

 test is best shown by the figures of a smaller specimen (PL 154, figs. 4~6)- Geni- 

 tal pores 4, well developed in both specimens. Ambulacrum III flush with the 

 rest of the test and with pores so small they can be made out only with a lens. 

 Ambulacra II and IV imperfectly petaloid, each petal about 10 mm. long, with 

 ten pore-pairs in posterior series but only four in anterior. Ambulacra I and 

 V more perfectly petaloid, each petal about 14 mm. long by 3.5 mm. wide, with 

 16 or 17 pore-pairs on each side; these posterior petals are distinctly curved, 

 diverging at first very evidently and then bending slightly inward (see PI. 158, 

 fig. 5). There is much coarse tuberculation and some rather large-sized tubercles 

 in interambulacra 2 and 3, but the large primary tubercles are found only in 



1 Mtxp6s = small + irkraKov = a petal, in allusion to the unusually small petals. 



