PLATE YL 



Genus Hemicystites Hall, 1852. 

 Hemwystites (s. g. Cystaster^) granulatus Hall^ 1871. 



Fig. 1. View of tlie summit of a specimen (enlarged to four diameters), showing 

 the rays, which preserve the external plates, with an oval depression at 

 the extremities, from which extends a narrow groove along the center 

 of the ray to the oral plates. The ovarian or anal pyramid is shown as 

 occupying the widest area. 



Fig. 2. A lateral view of another individual from which the exterior plates of the 

 rays have been removed. The ovarian pyramid preserves only the lower 

 range of plates. The specimen has been adherent to some foreign body, 

 ard the lower margin shows the cicatrix of attachment. (Enlarged 2^ 

 diameters.) 



Fig. 3. An oblique summit view of another individual less elevated than the preced- 

 ing, showing the rays and ovarian pyramid. In the three more distant 

 rays, the outer plates are removed, while they are preserved in the other 

 two. (Enlarged to 2i diameters.) 



Fig. 4. Lateral view of an immature (?) specimen, showing three of the rays denuded 

 of the upper range of plates. The body is more elongate and pointed 

 below, showing no evidence of having been attached. (Enlarged to three 

 diameters.) 

 These specimens are all from the collection of Mr. C. B. Dyer, of Cin- 

 cinnati, Ohio. 



AgELACRINUS {HE3IICYSTrrES) STELLATUS Hdll^ 1866. 



Page 215. 



Fig. 5. Summit view of a small individual, enlarged to six diameters. The rays are 

 short, preserving both ranges of plates, of which there are only from 

 seven to eiglit in each range. The ovarian pyramid is clearly defined and 

 the plates distinct. This individual, and a still smaller one attached to 

 the same shell, have an immature aspect. The plates are arranged in an 

 apparently imbricate order, as in the typical form of the genus. (En- 

 larged to six diameters.) 



Fig. 6. A summit view of a much larger individual (enlarged to four diameters) 

 from the rays of which the upper range of plates have been removed, 

 showing the character of the lower range, and the broad central groove. 

 In the upper left-hand area, the plates are shown to have an imbricating 

 arrangement. From the collection of Mr. C. B. Dyer. 



* A eac-like body, composed of minute plates and surmounted by five rays or ambulacra! areas, 

 each one consisting of two series of external plates separated by a narrow groove, and beneath these 

 a more distant series separated by a wider median groove. The structure and arrangement of plates 

 of the body has not been satisfactorily made out in this form, and, tlierefore, there may be some 

 doubt of its generic relations. The first specimens examined were su ii as to suggcft an immature 

 form of H. stellatus ; but the uniform character of a granular surface, without visible (or at most 

 very obscure) plates, suggettsa distii.ction. While the greater number of individuals show evidence 

 of having been adherent to some foreign body, a single one (fig. 4) appears to have been quite free. 

 Although a larger amount of materials would be desirable for examination bef. re deciding upon a 

 separation from Hemicystites, I would suggest for a provisioi al term the name of Ctstaster. 



