154 The Ottawa Naturalist. [Dec. 



contact of the first pinnules of adjoining arms, and about the 

 same distance measured transversely at the point of origin of 

 these pinnules. The larger of my specimens measures 30 mm. 

 and 15 mm. in these two directions respectively. It is therefore 

 apparent that the mature cup is more elongate than the un 

 developed form. 



In these specimens, the arrangement of the plates, the 

 character of the posterior interray, the peculiar manner of 

 origin of the first and second pinnulas and the biserial arms with 

 their three-jointed plumes conform exactly to the description 

 given by the authors cited. A further account of the anatomy 

 of the form is therefore quite unnecessary. 



With regard to the ornamentation, Billings states that "A 

 strong, rounded carina, or ridge, runs up each of the primary 

 rays, and, dividing into two on the centre of the third plate, 

 sends a branch up each of the secondary rays to the base of the 

 fingers; the carinse are also divided on each of the basal plates, 

 and coalesce into one on the centres of the first primary radial 

 plates; in the azygos interradius a sixth rib ascends to the top 

 of the cup, dividing the space into two parts about equal; it 

 bifurcates below on the centre of the large azygos, one branch 

 proceeding to the centre of the two contiguous first primary 

 radial plates." Billings further states that, with the exception 

 of these carinae, the plates are smooth. The description given of 

 the ornamentation by Wachsmuth and Springer is as follows: 

 "A small species. Dorsal cup obconical with slightly convex 

 sides ; section across the costals sharply pentagonal, owing to the 

 conspicuous radial ridges, which pass from the arms down to the 

 centre of the radials, where they divide and are continued to the 

 basals. The ridges, which are rounded, grow narrower towards 

 the middle of the plates, widening at their margins. Surface, 

 except along the ridges, covered with numerous small pustules 

 without definite arrangement." 



All the above features are exhibited by the present speci- 

 mens, but in addition, each plate of the cup, with the exception 

 of a iew of the higher brachials and interbrachials, is provided 

 with prominent ridges radiating from the centre to the sides of 

 the plate, where each is continuous with the corresponding ridge 

 of the adjoining plate. In the case of the basals, the radials, the 

 first brachials and the first interbrachials, these ridges coalesce 

 at the centres of the plates, are remarkably lineal in character 

 and are continuous across the sutures: higher up they become 

 more and more petaloid in character. On the outer sides of the 

 main carinae, where they pass from the radials to the basals after 

 bifurcation, lie secondary parallel ridges, which do not, however, 

 reach the centres of the plates. Somewhat irregularly, similar 



