No. 2.] MONTGOMERY — A DEVONIAN BLASTOID. 83 



cave plate (Fip^. 1 h.'). The lateral and superior opening has 

 been regarded as the anal aperture ; and the long, concave plate, 

 that tapers upwards and is quite prominent at its upper extremity 

 where it forms the inferior boundary of the anus, has been styled 

 the anal plate. The inter-radials of this area also differ in posi- 

 tion from those of the other four interambulacral areas, their 

 apices being directed downwards and reaching the radials at the 

 base of the calyx. 



On the superior surface of the specimen are to be seen five pairs 

 of little apertures placed in a circle, and usually considered to 

 have been genital in function ; whilst in the centre of this circle 

 and also of the summit of the calyx, is an aperture regarded as 

 the mouth, and provided with small protecting plates. Hence, 

 besides the foramina of the poral plates there are twelve openings, 

 viz : the mouth, ten genital openings and the anus. 



In comparison with Pentremites it is to be noticed that the 

 radials of Nucleocrinus are much shorter and the inter-radials and 

 pseudambulacra much longer than those of the former; that in 

 Nucleocrinus an anal opening is present in one of the interambu- 

 lacral regions ; an anal plate is also present ; and in consequence 

 of the situation of the anal orifice and the anal plate there is an 

 extra inter-radial or deltoid plate in the same area ; that the two 

 deltoid plates of this modified area are inverted in position ; that 

 the pseudambulacral fields are convex, and not concave, possess wel 1 

 marked pore-plates, and rather finely marked transverse grooves. 



As the modified interambulacral area is not exhibited in the 

 only figure given of lucina, i.e. Fig. 16, Plate 1, of the Fifteenth 

 Report of the Regents of New York State University, it is im- 

 possible for me to institute anything like a complete comparison 

 between lucina of New York and the Blastoid under consideration. 

 Still, on comparing the latter with the figure of lucina one cannot 

 fail to observe certain differences between them, in the lancet- 

 plates, the prominently arched radials at the lower ends of the 

 pseudambulacra, and the general shape of the calyx. The bring- 

 ing to light of other specimens may, in the future, prove, what I 

 strongly suspect, that this is a species quite distinct from lucina, 

 and hitherto undescribed. In such event, this being the first 

 species of Nucleocrinus discovered in this country, I would here 

 propose for it the specific name Canadensis. 



It is worthy of note that the genus Nucleocrinus in rocks other 

 than American has thus far been altogether unknown to science. 



