448 



DESCRIPTIONS OF SPECIES OF HELIASTER. 



the spines, Dr. Gray may possibly have meant flattened on top ; but 

 compressed spines iVo sometimes occur, and altogether, these features 

 are exceedingly variable throngliout the genus. 



A comparison of the specimens in question with a large series of He- 

 liaster Kubingii, from Lower California and the west coast of Mexico, 

 proves that these two species are identical, and as Dr. Gray's name has 

 priority, it must be used. 



This species is readily distinguished from the others by its less numer- 

 ous and ijroportionally longer free rays. The number of rays varies 

 from 15 to 2G, but only one specimen in the collection has fewer than 22 

 rays, 23 being the most common number. In nearly all the specimens, 

 both dried and alcoholic, the disk proper is more or less elevated above 

 the general contour of the abactinal surface, and is sometimes consid- 

 erably inflated, though usuall}* flattened on top. The free portions of 

 the rays vary greatly in length, being occasionally almost as short pro- 

 portionally as in some specimens of if. Jielianthus, and again may reach 

 nearly to the disk. The rays are stout, well rounded, and retain their 

 shape better than in the other species of the genus, due to the more 

 rigid character of the skeleton. They are well defined close to the disk, 

 their united portions being separated by deep channels, formed by the 

 convex surfaces of the rays. The measurements of three siiecimeus 

 will serve to explain the proportional dimensions of the different parts: 



Diameter of the dislc 



Longest radius 



Entire lenjith of rays 



Length of free portions of rays 



Specimen 

 from Lower 

 California. 



38 



The spines of the upper surface, although exceedingly variable, are 

 more or less characteristic of the species, in their size, shape, and ar- 

 rangement. Those of the disk proper and of the inner median i)ortions 

 of the rays are larger than the others. They are very stout, generally 

 much stouter than in any of the other species, sometimes exceedingly 

 irregular, very short clavate, cylindrical, or tapering ; the tips are broad 

 and flattened on top, slightly excavate, or more or less furcate, some- 

 times compressed, or tapering and rounded. On the disk they are dis- 

 tantly separated, sometimes nearly uniform in size and shape, at others 

 consisting of large and small intermingled, or smallest in the center of 

 the disk. 



On the upper surface of the rays, the spines form five radiating rows 

 or series. The lateral rows, one on each side, are rather low down, and 

 on the united portions of the rays are near together, though sometimes 

 wanting. These rows are the most regular of the upper surface, and 

 consist of the smallest spines, which are generally short, slightly taper- 



