214 



PAXAMTC DEEP SEA ECHINI. 



MOIRA A. Ag. 



Moira clotho A. Ag. 



Moera clotho Mich. Rev. et Mag. Zool. 1855. p. 247. 

 Moira clotho A. Ag. Eevision, p. 147. 



Plate 109. 



During the voyage from New York to San Francisco the " Albatross " 

 collected a few young specimens varying in size from 7 to 34 mm., at Stations 

 2800 and 2801. Unfortunately they came badly broken, but the fragments 

 sufficed to show that in the smallest specimen the adult features are already 



developed. The test is perhaps less angular 

 than in old specimens, but the sunken am- 

 bulacra, both the lateral and odd anterior, 

 are fully as developed as in larger speci- 

 mens. The radiolesof the different parts of 

 the test are as well differentiated as in larger 

 specimens, and in the younger stages both 

 the peripetalous fasciole and its subanal 

 branch follow the same course as in full 

 grown specimens, passing at a considerable 

 distance under the anus. The large suckers 

 of the antei'ior ambulacra are quite as 

 marked as those of the deep-sea genera Aceste and Aerope. In fact we 

 might look upon Moira as a further stage in the development of sunken 

 ambulacra ; Abatus having lateral ambulacra greatly developed, while 

 Cionobrissus and Aerope have a wide anterior ambulacrum more like that 

 of the Schizasteridse. 



Among the Spatangoids with deeply sunken ambulacra like Abatus, 

 Aceste, Moiropsis, and Moira, the last is specially noted for the modifications 

 produced on the abactinal system by the great width of the deeply sunken 

 anterior ambulacrum and the deeply sunken petals of the adjoining lateral 

 anterior ambulacra (PI. 109, figs. -2, .'-il). The apical system. Fig. 312, 

 consists of two narrow elongated plates, which are united along the medium 

 suture of the odd posterior lino of the interambulacrum and form an arc 

 extending from the anterior oculais. There are two large genital pores 



Fig. 312. Moika clotho. 



