69 



finely striated joints; having a contracted circumference of articulation. Its 

 column has sometimes numerous joints (hg. 18.) swelling gradually out, and 

 thus giving it a barrel-shaped appearance, generally pressed in on one of its 

 sides, and becoming there concave, with a central perforation evidently leading' 

 to the alimentary canal. This has all the appearance of acicatrized wound, and 

 as the alimentary canal in the column is not increased, the swelling can only 

 arise from a more rapid secretion from these joints, probably to strengthen it, 

 and to compensate thus for the injury probably sustained in one of its auxiliary 

 side arms. The cavity before mentioned, was probably produced by the loss 

 or separation of the stump of the injured auxiliary side arm from the column, 

 and the subsequent cicatrizing of the wound. 



The BASE of the column is probably similar to that of the genus Cyatho- 

 crinites, which will be hereafter described. 



The PELVIS (fig. 8.) On the superior columnar joint rest, as far as I have 

 been able to ascertain, five plate-like joints, which I consider, though with 

 some hesitation, (for reasons stated in the note, page 67.) as forming the pelvis. 

 At their lower surfaces they are smooth, but have a transverse subtriangular 

 ridge, with a central perforation and a narrow lip-like extension. Their lateral 

 surfaces are slantingly truncated to admit the intervention of a muscle. A ridge 

 divides the upper surface into two angularly slanting planes, having each a 

 transverse ridge perforated by a nourishing vessel, and showing a lip-like pro- 

 cess near the inner surface. The superior and inferior surface is, near Ihe ex- 

 terior circumference finely striated for tlie adhesion and transmission of muscu- 

 lar portions, connecting with the exterior muscular covering of the crinite, and 

 capable of producing on contraction numerous minute tubercles, which may be 

 observed in well preserved specimens. 



The FIVE INTERCOSTAL PLATE-LIKE JOINTS (fig. 6. 7. 9. the animal having no 

 costals), are oblong and hexagonal, one of them being somewhat longer, and hav- 

 ing one of the sides of its superior surface considerably larger. They insert 

 their inferior angle into the five angular spaces formed by the plate-like joints of 

 the pelvis, articulating to them by nearly .similarly marked surfaces. They pre- 

 serve externally the subconical figure, and thus enlarge the abdominal cavity. 



The SCAPULA (fig. 2. to 5.) are inserted into each of the superior angles of the 

 intercostals. They are thin, plate-like, and subpentagonal, adhering by subtrian- 



