CLARK: BRITTLE-STARS. ' 277 



genus is to be maintained. Close comparison of the Calbuco and 

 Talcahuano specimens shows convincingly that they are the same 

 species. There is absolutely no other tangible difference than the 

 complete absence of marginal papillae in the Talcahuano specimen. 

 The latter, Lyman states (1875, Illus. cat. M. C. Z., no. 8, pt. 2, p. 20) 

 "agrees well" with Miiller and Troschel's type at Berlin. No doubt 

 the Calbuco specimen has also been compared with that type. There 

 is no reason therefore for doubting the identification of these brittle- 

 stars. The real problem is as to the significance of the marginal 

 papillae in the largest specimen. If their presence is merely a matter 

 of individual diversity, then the line between Amphiodia and Ophio- 

 phragmus becomes very difficult to maintain. If on the other hand, 

 it is an indication of maturity and their absence in the smaller speci- 

 mens is because the full specific character is not yet assumed, then 

 we have an interesting case of growth-change. That the latter is the 

 correct interpretation is indicated by the appearance of the papillae, 

 some of which are still very small, and by the fact that Miiller and 

 Troschel's specimen was only 6 mm. across the disk, the Hassler 

 specimen is about 7.5 mm., and the specimen from Calbuco is almost 

 9 mm. Of course, the final determination of the question must await 

 more abundant material. Meanwhile the opinion expressed (1910, 

 Bull. M. C. Z., 52, p. 341) that Amphiodia chilensis is a southern 

 species reaching northward to Peru seems untenable, as all other 

 species of Ophiophragmus are tropical or subtropical in their occur- 

 rence. 



Ophiophragmus lutkeni. 



Amphipholis lutkeni Ljungman, 1871. Ofv. Kongl. vet.-akad. Forh., 28, 



p. 636. 

 Amphiodia lutkeni Koehler, 1915. Bull. 84 U. S. N. M., p. 69, pi. 6, fig. 1, 2. 



Koehler's admirable description and figures make it possible to 

 determine beyond doubt, specimens of this interesting species, which 

 has hitherto been known only front the unique t^pe, taken nearly 

 fifty years ago by Dr. A. Goes at Tortola, Virgin Islands, in 10 fms. 

 I found the species fairly common at Sandy Point, in Buccoo Bay, 

 Tobago, where it occurred buried in soft, sandy mud in two or three 

 feet of water, in company with 0. septus, Ophionema intricata, and 

 species of Amphiodia. My largest specimens are of about the same 

 size as the holotype, the disk measuring 5-6 mm. across and the arms 

 80-90 mm. in length. This species has the habit common to many 



