44 The Ottawa Naturalist. [June-July 



arrangement of the plates is not clearly shown, but apparently 

 a fourth pair of interbrachial plates continue the interray to 

 the margin of the cup. 



The characteristic features of the species lie more particu- 

 larly in the ornamentation of the cup plates. From the centre 

 of each radial a strongly marked carina runs up the ray to the 

 middle of the second costal, where it bifurcates and continues 

 over the distichals to the point of origin of the arms. A strong 

 ridge-like carina with sharp, square shoulders connects the 

 centres of the radials, and forms a very characteristic, sharply 

 defined band passing around the cup in this zone. Downwards 

 from the centre of the radial, the carina is broken into two halves, 

 each of which passes to the contiguous basal. No other stellate 

 ornamentation appears on any of the plates, except a faint radial 

 striation on the first interbrachial. All the plates, however, 

 are marked with a distinct granulation which is more pronounced 

 on some plates than on others. 



The stem. The stem is composed of thin discs which are 

 alternately large and small. Near the cup, the larger joints 

 are about two mm. in diameter and occur to the number of 

 three in the space of one mm. Distally, the stem tapers rapidly 

 and the joints become more elongated. Externally the stem- 

 joints are round in section: the shape of the internal passage 

 was not observed. 



The arms. The arms are ten in number: they appear to 

 become free and to be provided with pinnules beyond the second 

 distichal. The joints are distinctly uniserial in arrangement 

 and occur to the number of three in the distance of one mm. 

 in the lower portions of the arms. Bifurcation of the arms 

 was observed in one instance only: the division in this case 

 occurs above the sixtieth joint. The present species is dis- 

 tinguished, more particularly, by the strong carina passing 

 around the cups in the radial zone. The lack of stellate orna- 

 mentation on the interbrachial plates distinguishes it from 

 G. decadactylus and G. dyeri, which are, moreover, Cincinnatian 

 forms. 



The species of Glyptocrinus hitherto described from the 

 Trenton of Ontario are G. ramulosus, G. omatus and G. margin- 

 atus: none of these shows a prominent carina encircling the 

 cup. The small basal plates and slender branching arms of 

 G. ramulosus sufficiently differentiate that species. The striking 

 ornamentation of G. omatus, which consists of five or six con- 

 spicuous, finely striated ridges radiating from the centres of 

 the plates, serves to distinguish it from the present species. 

 The margined plates of G. marginatus and the different arrange- 



