18 Dr . T. Wright on new Species of Echinodermata 



The imperfect condition of the shell prevents us from ascer- 

 taining the precise number of these tubercles there were in each 

 row, but judging from the number (eight) contained in an im- 

 perfect column, we suppose there could not have been less than 

 from twelve to fourteen ; they increase gradually in size from 

 the mouth upwards, and are of a moderate magnitude when 

 compared with the shell they adorn. The areolas are small and 

 not prominent, and the tubercles are deeply perforated. The 

 space between the two rows of tubercles is wide and filled with 

 close-set miliary tubercles, most of which are raised on eleva- 

 tions, and have their summits perforated; these all support 

 small spines, which are well preserved in situ in our specimen. 



The spines are of two kinds those articulated with the large 

 tubercles (the primaries), and those articulated with the small tu- 

 bercles (the secondaries). The primary spines exhibit a peculiar 

 structure : the head is large, increasing gradually in diameter 

 from the articulating cavity to the circular band ; the rim of the 

 acetabulum is coarsely and deeply crenulated, and the raised band 

 is prominent, narrow, and finely milled ; the neck tapers gradually 

 from the band to the point where it joins the stem, which has the 

 same structure as the head, and its surface is delicately sculp- 

 tured with fine longitudinal lines ; the stem is united to the 

 neck by an oblique harmonia suture. The structure of this part 

 of the spine differs from that of the head and neck; in the 

 spines denuded of their external layer, it has a horny semi- 

 transparent appearance ; in those in which this layer is pre- 

 sent the surface is sculptured with longitudinal lines of micro- 

 scopic delicacy, and there are numerous small processes, having 

 their points directed forwards, arranged with some regularity in 

 rows. The stem is circular or slightly compressed; but as 

 none of the spines are complete, a part having been broken 

 off, we are unable to ascertain their length. The secondary 

 spines are very uniform in size and structure, and are abun- 

 dantly preserved in situ ; they measure from /pths to ^ths of 

 an inch in length and are round, and have their surface orna- 

 mented with fine longitudinal lines. The mouth is armed with 

 a powerful dental apparatus : three of the jaws are very promi- 

 nent ; the external surface of each is strengthened by three pro- 

 minent ridges ; the teeth are large, but are fractured. As the 

 under surface of the test only is shown, we are unable to describe 

 the ovarial disc and the dorsal surface thereof. 



Affinities and differences. This Urchin belongs to the same 

 group as C. Fowler i and C. maxima, Goldf. It resembles the 

 former in the form and structure of both areas, and in the gra- 

 dual development of the primary tubercles from the mouth 

 upwards. It is distinguished from that species, however, by the 



