2 BULLETIN 74, UNITED STATES NATIONAL MUSEUM. 



DESCRIPTIOX OF SPECIES. 



CALOCIDARIS MICANS (Mortensen). 



Plate I; plate 14, figs. 5-G; plate 15, fig.'i. 1-2, 7; plate 10, fig.-*. 3-5, 7-8, 10, 13-14; plate 17, figs. 7, 12-13. 



DorocidarU (?) micans Th. Mortensen, /?i9o// Echinoidea, pt. 1, 1903, p. 23, pi. 9, fig. 26; pi. 



11, fig. 24. 

 Calocidaris micans IT. L. Clark, The Cidariche, liull. .Mas. ("omp. Zoijl., vol. 51, 1907, p. 211, pi. 3. 



Two specimens of this very beautiful cidarid were received for examination 

 from the U. S. National Museum, and form the basis of the following description. 

 They were dredged at Alhatross stations 234S and 2.354. The very beautiful speci- 

 men figured on plate 1 I have not examined in detail. It is the specimen mentioned 

 by Clark as "the most beautiful echinoid" he has ever seen. The photograph 

 was made at the U. S. National Museum. 



Measurements. 



a The figures within the parentheses indicate the height from the mouth opening 

 to the anal opening: the other figures indicate the height of the corona. 



The test is high, the height of the corona being from 72 to 75 per cent of the 

 horizontal diameter; the sides are regularly curved, not flattened above or below; 

 the edge of the peristome is not incurved; the peristome and apical system are not 

 flattened, but rise in continuation of the curvature of the corona, which makes 

 the whole test appear almost spherical. 



The ambulacra are in the two specimens 20.9 per cent and 23.1 per cent of the 

 interambulacra in width (Clark gives 25 per cent); each ambulacra! plate carries 

 inside the j)rimaiy tubercle a secondary tubercle of almost equal size in the middle 

 of the plate (Plate 14, fig. 6); a verj'- small tubercle is found at the lower edge of 

 the plate between tlie two larger tubercles; there are thus four longitudinal series 

 of tubercles in the interporiferous zone, except cjuite near the peristome and a 

 somewhat larger part at the abactinal end, where the inner tubercle is found only 

 on one side, irregularly alternating; at the upper end it has not appeared as yet. 

 There is scarcely a distinct, naked median line, and Clark's "nearly bare median 

 ambulacral areas" is not an adequate expression for the specimens at hand; the 

 specimen figured by Clark also appears to have distinct inner series of tubercles. 

 The above description is based upon the larger specimen; in the smaller specimen 

 the inner tubercle has not yet appeared on both sides, even at the ambitus, but 

 stands irregularly alternating, now on several plates in succession on one side, then 

 on some plates on the other side, and so on, quite irregularly. In this specimen 



