M r. T. H. Stewart on the young state of Ophiocoma rosula. 389 



Within the stomach were seen ten attached chib-shai)ed bodies' 

 similar to the membranous tentacula of the arms, which were in 

 constant motion ; two were attached between each dark bundle 

 of spines, or oral cluster, which are situated at the mouth of the 

 disk. They seemed to be contractile, and to draw back to the 

 sides of the stomach, assuming a somewhat globular form. 



But what I desire more especially to direct attention to are the 

 spines on the rays ; these may be said to be of three kinds : — 

 1st, those which may be termed palmate or basal spines of the 

 ray, or the first set at the part where the ray springs from the 

 disk (fig. 4) ; 2ndly, the reticulated spines (fig. 5) ; Srdly, the 

 hooked spines (fig. G). 



The first set are shaped somewhat like a hand with the fingers 

 spread out, only minus a thumb : as the greater number have 

 only four spinules, or secondary spines, these are longer and 

 more widely separated from each other than in the second set, 

 and consequently the whole spine is broader. It has a broad, 

 thick, and rounded base, and immediately above the base the 

 spine is narrowed, and then becomes wider again so as to form 

 a constriction at this part ; and in fact the spine may be divided 

 into three parts, — the base, the body constricted at the lower 

 part, and the spinous extremities. 



The palmate portion of the spine is pierced with irregular 

 holes. The entire spine is covered with a delicate membrane, 

 and this connects the spinules, forming a web, thus giving the 

 spine a strong resemblance to the foot of a frog. In other parts 

 of the spine this membrane is closely attached to it ; and where 

 the webbing occurs, the two parts covering the upper and lower 

 portions of the spine come in contact, and thus as it were en- 

 close it in a membranous sac. This membrane is destroyed by 

 boiling in caustic potash. 



The spines of the second set may be said to occupy rather 

 more than the lower two-thirds of the ray on the under side, and 

 almost the whole of the u})per. They arc more irregular in their 

 form than the last, especially as regards the number, form, and 

 arrangement of the spinules. Their base is not so rounded and 

 the constriction not so well marked as in the first set. In fact, 

 the spine altogether is not so symmetrical and constant in its 

 shape as either of the others, and is evidently in a transition 

 state, for no two of these spines were alike in form, whilst the 

 first or ])almate, and the third or hooked, never varied to any 

 marked extent. In the adult animal, the hooked spines still 

 preserve the form that they had in their young condition, though 

 of course they are proportionately larger. 



As the second set of spines grow, they become more regular 

 in form, and the spinules, or what are then the rough serrations, 



