178 



Mr. J. E. Gray's Synopsis of 



of the Starfishes as it is in the external tessera? of the Sea Eggs, and 

 in the spines of both these kinds of animals, as they are often to be 

 found broken and repaired during their growth, and this repair does 

 not take place by any secretion applied to their surface, but by a 

 healing of the part, which leaves a scar on the surface. Neverthe- 

 less, the entire similarity which exists between the external spines and 

 the internal tubercles at once shows that they are of the same struc- 

 ture ; and this is further proved by the examination of the tubercles 

 of those kinds which are in great part exposed on the surface, as is 

 the case with the different kinds of Pentaceros, where the development 

 of these hard parts can often be observed during the process of re- 

 producing an arm that has been accidentally injured or destroyed. 



The specimens described in this synopsis are either in the collec- 

 tion of the British Museum or in that of the Zoological Society, 

 which includes the specimens discovered by Mr. Cuming during his 

 residence in South America, and presented by him to the Society. 



Order 1. Asteroida. 



Body free, star-shaped, with distinct small ambulacra (or walks) 

 of double pores on the oral surface, from the mouth to the ends of 

 the rays ; dorsal wart distinct. 



These animals have the faculty of reproducing the arms or such 

 parts as may be accidentally broken oft ; and if an entire arm be 

 separated, provided part of the body be attached to it, other arms 

 are reproduced, and a fresh perfect animal formed. 



Sect. 1. The Ambulacra with four rows of feet ; dorsal wart sim- 

 ple. 



Family 1. Asteriad^e, Gray, Syn. Brit. Mus. 62. 

 1. Asterias. 



Skeleton netted with a single mobile spine at each anastomosis of 

 the ossicula ; body covered with more or less prominent elongated mo- 

 bile spines*. 



a. Rays 12 or 13, slender, tapering, with small elongated spines. 



1 . Asterias Aster, Gray. Rays 3 times as long as the diameter 

 of the body ; back with 7 series of spines, the labial spine at the an- 

 gles of the arms very long. 



Inhab. . Brit. Mus. 



* Some continental zoologists have objected to the shortness of my ge- 

 neric and specific characters ; and I therefore think it right to observe, that 

 it does not seem to me either necessary or desirable to give more than the 

 essential distinguishing marks, in a monograph founded on the complete 

 analysis of a large collection of species. On the other hand, it appears to 

 me to be quite right, in the publication of a single supposed new genus or 

 species, or of a limited number of them, where the author either wants the 

 materials or the time for a rigid examination of the entire group, to give all 

 the assistance that can be derived from a detailed description. No natu- 

 ralist will doubt which is the easier process ; and few, 1 think, will hesitate 

 as to which is the most advantageous to science. 



