122 NATURAL HISTORY BULLETIN 



The most distinctive feature is the presence of a pair of defin- 

 ite dorsal muscle bands in the rays, extending from near the 

 base to the tip and enabling the rays to be bent strongly upward 

 with great facility. The order Notomyota was based on this 

 character, as the name implies. 



The large pectinate pedicellariae, with numerous incurved pa- 

 pillae, sometimes arising from and between two plates, are also 

 characteristic of this group, but they are sometimes lacking, 

 especially in the young. 



Family Benthopectinid^ (Verrill) Fisher. 



Benthopectinidce and Pontasterinm Verrill, Trans, Conn. Acad. Sci., x, pp. 



200, 217, 1899. 

 ParachasteridcB Sladen, op. cit., 1889, p. 4. 

 BenthopectinidcB Fisher, 1911&, p. 120. Verrill, op. cit., p. 310, 1914a, 



An almost strictly deep-sea family. Form stellate ; disk rather 

 small ; rays five, elongated, with two rows of thick, spinose, mar- 

 ginal plates, which are not exactly paired, but are sometimes 

 alternate, or nearly so. Adambulacral plates are angular and 

 have elongated furrow-spines and one or more enlarged actinal 

 spines. 



The species of this family are numerous and occur in all 

 oceans, but they are nearly all deep-sea species. Some of them 

 extend to the greatest depths from which stai-fishes have been 

 obtained. Only a few occur in depths less than 150 fathoms, 

 none are found in very shallow water. 



Those genera that have an impaired interradial marginal plate 

 were formerly placed by me in a special family, BenthopectinidcB, 

 later reduced to a subfamily, Benthopectininm. The discovery of 

 certain deep-sea species that vary in this respect, and others that 

 are intermediate, renders it useless to longer maintain such a 

 subfamily group. BentJiopecten spinosiis Ver. occurs in very 

 deep water off the Atlantic coast of the United States. Other 

 species occur in all the oceans. 



It is represented in the West Indies by B. simplex (Perrier), 

 which occurs in 1323 fathoms (Blake Exped.). Redescribed in 

 detail (op. cit., 1894, pp. 254, 256) as Pararchaster simplex. It 

 was described from a very young specimen. 



