io6 DISCOVERY REPORTS 



As detailed under "Remarks", Odontaster penicillatus appears to be a composite of 

 several formae. The problem is complicated by the absence of figures of Philippi's 

 type specimen whereby the type form may be identified. In the absence of this informa- 

 tion, the type form is assumed to be that described and figured by Sladen as Gnathaster 

 pilulatus. As a matter of fact it may well be one of three others analysed in the sub- 

 joined key. Similarly, the type form of Odontaster grayi is assumed to be that with 

 narrower superomarginals, as figured by Koehler, 1912, pi. 11, figs, i, 2. 



The following synopsis may be of aid in distinguishing the principal varieties, though 

 this will not be easy without an extensive series of specimens for comparison. 



a^. Forma penicillatus. Form stellate, the breadth of ray at base equal to or less than the length 

 measured along side; marginal plates 11-21 according to size of specimen; see "Remarks". 

 b^. Central spinelets of paxillae conspicuously larger than marginal spinelets; paxillae 

 distinctly spaced. 



c^. Superomarginal plates narrow (Sladen's figure oi pilulatus). St. WS 84. 

 c~. Superomarginal plates patently heavier and broader than in Sladen's figure of 

 pilulatus. St. WS 776. 

 b-. Central spinelets of paxillae not conspicuously larger than median spinelets, usually 

 slender; paxillae not spaced. 



c^. Superomarginal plates slightly narrower to slightly broader than in Sladen's figure 



oi pilulatus; breadth of proximal plates equal to length of i|-if plates. St. WS 98, 



WS 756A. 



c^. Superomarginal plates broader and encroaching more upon paxillar area; breadth 



equal to length of 2-2^ plates. St. WS 848. Here also would go 8 specimens with 



broad, rather coarsely granulate, superomarginals; form stellate; superomarginals 



13-15. They are more stellate than the general run oi grayi, yet appear more closely 



allied to that form on account of the low number of marginals. The body form is 



that oi penicillatus. In the register of specimens they are entered as "intergrades". 



a^. 'Povmz. grayi. Form pentagonal to stellate-pentagonal ; rays broader at base than length along 



the side; marginal plates upward of 17; see "Remarks". 



b^. Superomarginal plates narrow (Koehler, 1912, pi. 11, fig. 2) to medium broad. These 



intergrade with b^; usually but not invariably larger specimens. St. WS 83, WS 86. 

 b". Superomarginal plates broad (Koehler, 1912, pi. 12, fig. 9). 



c^. Superomarginal and to a less extent paxillar spinelets granuliform in appearance; 

 actinal spinelets coarser; specimens usually small, although the largest specimen of 

 f. grayi (R 42 mm., St. WS 765) falls here. 

 c"^. Superomarginal spinelets slender, close-set three times as long as thick; paxillae 

 small, widely spaced, with slender delicate spinelets; actinal spinelets long and 

 slender. One specimen, arcuately stellate-pentagonal, R 42 mm., 15 superomarginals, 

 St. WS 825. This specimen has 3 teeth to each mouth angle and falls in Koehler's 

 Epidontaster but appears to be a variant of forma grayi. 



Remarks. The extensive series of specimens has revealed a very considerable range of 

 variation. Some of these specimens satisfactorily bridge the gap supposed to exist 

 between Odontaster penicillatus Philippi (O. pilulatus Sladen) and O. grayi Bell. In the 

 species known as grayi the body shape ranges from pentagonal, usually slightly to 

 decidedly "arcuate" (Koehler, XI, 2^), to broadly stellato-pentagonal, there being, 



1 These references are to Koehler, 1912, pis. 11 and 12; Koehler, 1920, pi. 39; Sladen, 1889, pi. 57. 



