BARBADOS-ANTIGUA REPORTS 109 



teeth; the general form of the valves is very similar to that 

 found in C. rod^ersii (See Mortensen, 1904. Siam Ech., pi. IV, 

 fig. 19) except that in the Australian species there are six ter- 

 minal teeth. 



Peristome nearly white, but thick skin near mouth, tube-feet 

 and gills yellowish. Pedicellariae pale reddish-yellow. From 

 below ambitus upward the epidermis becomes thicker and stead- 

 ily more and more pigmented until on the periproct it is quite 

 black, especially at center. Primary spines whitish or glassy 

 with 2-5 ill-defined but very distinct bands of red ; the shade of 

 red is between nopal-red and garnet-brown of Ridgway's pi. 1 

 (Color Standards and Nomenclature, 1912), and is quite free 

 from any violet or purple tinge. The little club-shaped prima- 

 ries on the abactinal plates have their distal halves bright rose- 

 purple in striking contrast to their surroundings; the shade is 

 very near the rhodamine purple of Ridgw'ay's pi. XII. 



Holotj^pe from Station 101. June 13, 1918. On Shoal Bank, 

 about 3 miles W. of Needham Point, 25-40 fms. Sponge bottom. 

 Dredge. 



It is a great pity that only a single specimen of this pretty 

 little urchin was taken, for the genus, although occurring on the 

 western coast of Mexico and also in the Mediterranean, has never 

 been found hitherto in the West Indian region. Moreover it is 

 probable that this is a very young specimen and it would be 

 interesting to know to how large a size the species grows. The 

 Australian species, rodgersii, is the largest, reaching a diameter 

 of 100 mm., while the Mediterranean and Mexican species attain 

 less than half that size, so far as we yet know. Neither species is 

 at all well known. In every way, the West Indian species is 

 nearest to that of the Mexican coast (coronatus) but it differs in 

 several minor particulars. The coloration is noticeably different 

 for in coronatus, the red which bands the spines is distinctly 

 purplish and there is no trace of purple on the primaries of 

 ruhicingulus. ^More important is the difference in the globiferous 

 pedicellariae; in coronatus, the narrow part of the blade is short 

 and the terminal teeth are very long (see A. Agassiz and H. L. 

 Clark, 1908, Mem. M. C. Z., 34, pi. 51, figs. 18, 19) while in 

 ruhicingulus, the narrow part of the blade is longer and the 

 teeth are very much shorter. Of course, more material is needed 



