32 PLATYCEINIDJL. PLATYCRINITES. 



But when opened the integument was withdrawn on each side, leaving the orifice 

 uncovered. 



The Rays. — On each of the perisomic ray-bearing pUites the cuneiform joint of the 

 ray articulates. On the sloping faces of these basal ray joints rest two other joints, 

 from which the first divisions proceed. These are succeeded by an equal nvunber of 

 cuneiform joints, which send ofl' fi-om their outer slopes the first tentaculated rays ; their 

 inner faces have each two joints resting on them, the upper of which are cuneiform. 

 Each of these joints support two other tentaculated rays. It wUl be seen by this 

 formida that the final divisions of the rays amount to thu-ty. The rays are arranged 

 around the abdominal bulb in five groups, six in each group. They are thicker in pro- 

 portion to the size of the animal, than in the typical species. But tliey terminate in a 

 similar manner, in delicate fine joints. 



The figure 1. a, PI. 3, will shew that the progressive increase in the size of the rays 

 commenced at the base, and gradually extended upwards. On reference to the plate it 

 will be seen that the growth of the lower joints, in the younger specimen, was already 

 considerable before the secondary series exhibited equal signs of increased dcvelopement. 

 This specimen also proves that, in the earlier stages of growth, the number of rays were 

 as constant as in the more matured animal. Of this we shall hereafter produce abun- 

 dant proofs in other genera. 



The Tentacdla. — The tentacula are equally numerous in this, as they are in the 

 typical species. 



The Column. — The column is circular at and near the dorso-central plate, but becomes 

 elliptical as it recedes from that point. It is somewhat thicker than in the typical 

 species, but it presents precisely the same modifications of structure ; therefore to enlarge 

 upon it would only be a repetition of all that was advanced when describmg the kevis. 



The Auxiliary Side Arms — are similar to those of the tji^ical species. 



The Base of Attachment — unascertained, but probably composed of indurated 

 fibrous root-Uke organs, by which it was moored to the rocky bed of the ocean. 



From the P. triqinUrhictylus possessing the same number of rays as the rnr/osus, it 

 may possibly be mistaken for that animal, though the latter presents characters suffi- 

 ciently distinct, if they are attended to, to prevent error. The rugged tumid plates 

 of the riigosus are alone sufficiently specific, for we altogether dismiss Miller's theoretical 

 opinions as to the elevations on the plates proving the muscularity of the calcareous 



