■246 Th. Mortensen. 



The peculiar shape of the oralia would appear to be a character 

 of specific value; in the Pentacrinoid oï Hathrometra Sarsii thej^ are 

 described by M. Sars (Mémoires pour servir à la connaissance des 

 Crinoïdes vivants, 1869, p. 48) as being convex, with only the point 

 „garni de très petites pointes coniques proéminentes"; in the figures 

 no trace of any concavity of the orals is seen. On the other hand 

 I find the oralia of the same shape, with the side-edges and apex 

 turned outwards, in the Pentacrinoid of Hathrometra tenella (of 

 which Mr. Grieg, Bergen, has most kindly lent me a few specimens 

 for examination — and H. tenella is regarded as synonymous with 

 H. Sarsii by Grieg), Heliometra glacialis and Aniedon petasus, as also 

 I find a slight indication thereof in some Pentacrinoids of Antedon 

 mediterranea, for which I am indebted to Dr. H. C. Chadwick. 

 W. B. Carpenter likewise describes and figures the oralia in the 

 species studied by him as somewhat concave, though not so much 

 as in this species. It is then not improbable that this shape of 

 the oralia will prove to be the rule among the Pentacrinoids of free 

 Crinoids, and one can scarcely help suggesting that it likewise holds 

 good for Hathrometra Sarsii, though it is hard to understand, how so 

 conspicuous a feature has been overlooked by so eminent an obser- 

 ver as M. Sars. The peculiar shape of the oralia in these Penta- 

 crinoids reminds one of those of Hyocriims (comp. P. H. Carpenter. 

 Stalked Crinoids of the Challenger. PI. VI). 



Infrabasalia do not appear to exist in this species. Anything 

 recalling the figures 52— 53, PI. 47 of Bury 's Memoir on "The early 

 stages in the Development of Antedon rosacea" (Philos. Transact. 

 Vol. 179, 1888) is not to be seen. I have also carefully isolated the 

 plates of the calyx under the microscope by applying cautiously 

 Eau de Javelle in alcohol, so that I am sure no small plates have 

 escaped my notice; but no trace of infrabasalia was found. If they 

 are represented at all in this species, which does not seem probable, 

 they must then already in this stage have been resorbed. A coales- 

 cence with the upper stalk-joint is excluded, since a considerable 

 number of joints are yet to appear between the calyx and the upper- 

 most joint of this stage. 



It should also be pointed out that in this stage the sacculi have made 

 their first appearance, viz. one in each radius, as seen in PI. IX, Fig. 1. 



The Stage II of Sars, comprising the development of the 

 radialia I — III, I have subdivided in II a, distinguished by the 

 appearance of Radialia I, and II b, in which also Radialia II — III 

 have appeared. 



Stage II a. This stage, characterized through the radialia I having 

 appeared, is represented by 3 specimens found attached, one to the 



