150 NATURAL HISTORY BULLETIN 



The jaw-plates are large and bear marginal and actinal series of 

 slender spines. 



The bilobed papularia often form a rather diffuse group on the 

 basal part of the ray and on the disk; the two halves are sep- 

 arated by the median row of plates between which papulae do not 

 often occur. The papularia are not swollen. In the adult the 

 papulae may be very numerous; few in the young. 



The dorsal muscular bands, in the few species examined, are 

 attached proximally to a crest-like process of two ambulacra! 

 plates, as well as to the inferomarginals. Professor Fisher thinks 

 this is a constant generic character. Other than this there are 

 no definite or precise characters to distinguish this genus from 

 Cheiraster. It may eventually be necessary to reunite them, un- 

 der Cheiraster. 



Personally I have not seen any West Indian species that can 

 be referred with certainty to Luidiaster. 



The description of the genus is given here mainly for the sake 

 of comparison with Cheiraster and Pectinaster, but also because 

 one of the above species (P. vincenti) has been referred to it by 

 Ludwig. 



The new species, Cheiraster enoplus, described above, has the 

 outward appearance of Luidiaster, and may eventually prove to 

 belong to that genus, when its dorsal muscles can be studied. 

 At present it is better to leave it in Cheiraster, for it has all the 

 external characters of the latter. 



Suborder Paxillosa (Perrier, emended). 



Perrier (as an order), Exped. Traiv., pp. 28, 192, 1894. Verrill, Trans. 

 Conn. Acad., x, pp. 199, 200, 201, 1899; op. cit., 1914o, p. 314. Fisher, 

 1911&, p. 19. 



These are Phanerozona in which the two rows of marginal 

 plates are usually well developed and often spinose, (in Luidia 

 only the lower are well developed). They usually have well 

 marked fasciolated grooves between them, to convey water for 

 respiration. The dorsal or abactinal plates are usually devel- 

 oped in the form of true, columnar paxillae or spinopaxillae ; 

 sometimes as parapaxillge or pseudopaxillaB. Pedicellariae are 

 often present, usually consisting of several connivent papillae. 



