264 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



and Brazil (the so-called picta). In this connection I would call attention to a speci- 

 men from Mauritius in the Berlin Museum (No. 1083; see p. 298) in which the cari- 

 nation of the arms is very greatly developed, as in certain specimens from Rio de 

 Janeiro, each carinate process bearing a tuft of fine spines. African specimens are 

 rather more likely to be uniformly colored than are those from Brazil, which makes 

 them appear to be different; but the presence or absence of yellow markings, though 

 altering the appearance of the individuals, is of not the slightest systematic significance 

 in this group. It is probably, at least for the most part, simply a response to local 

 conditions of illumination. 



The form which I have called indica is a well-marked local race of carinata 

 confined so far as we know at present to western Ceylon and the adjacent portions 

 of southern India and distinguishable by the small, short, and usually numerous cirri 

 with relatively short segments. The brachial carination is less developed than in 

 the majority of specimens of carinata and is never strongly developed. 



The form from the eastern coast of India (? and eastern Ceylon) reaches a larger 

 size than the others. In this form, clarki, the cirri are relatively larger with usually 

 more numerous segments and the brachial carination is obsolescent and entirely, or 

 almost entirely, absent in the distal half of the arms. This form is intermediate 

 between typical carinata and the large smooth ajra occurring from northern Australia 

 to Japan. 



The occurrence on the eastern coast of India of a form intermediate between 

 carinata and afra renders it highly improbable that any representative of the carinata 

 type occurs farther eastward than Java — if indeed it is really represented there. 



In the light of this inference the specimens supposed to be from Polynesia were 

 reexamined. They were foimd to represent carinata, agreeing in all respects most 

 minutely with others from Rio de Janeiro. They were undoubtedly collected by the 

 United States Exploring Expedition during its stay at that port and subsequently 

 mislabeled (see p. 319). Carpenter's record from Norfolk Island was probably based 

 upon some misapprehension, as no specimen exists from that locality (see p. 287), and 

 the record from the Bonin Islands seems to rest upon a young individual of T. afra 

 macrodiscus. 



The two large forms, aJra and macrodiscus, undoubtedly represent the same spe- 

 cific type — afra. Whether macrodiscus should be differentiated as a recognizable 

 subspecies or simply merged with afra is as yet a matter of personal opinion. Pending 

 the study of additional specimens of typical afra I have preferred to let macrodiscus 

 stand as a northern subspecies. 



In 1910 I wrote that the larvae of Echinus are highly specialized pelagic plutei, 

 those of Antedon almost annehdan in character and with a greatly reduced duration 

 of free existence. This would seem to indicate a great phylogenetic difference. But 

 the species of Antedon are of exceedingly limited range. Those of Tropiometra have a 

 very wide range, necessitating a prolonged free-swimming stage. Are we not justified in 

 saying that the larvae of Tropiometra may turn out to be plutei or something like them? 

 Mortensen said that, though this suggestion stimulated his interest in investigating 

 the early stages of Tropiometra carinata, the results of his study did not bear out my 

 expectation. He wrote that he expected that some day a crinoid may be found with 

 a truly pelagic larva resembling a pluteus or a bipLnnaria, but he thought it more 



