51 



of these parts of the animal ; another curious fact is also proved by them, 

 namely, that the animal had the power of reproducing them when broken. Thus 

 in the late Mr. TOBIN'S, specimen, a joint broken transversely near the summit, 

 is seen to have pushed forth a small hook and three other joints. (PL. n. fig; 

 18. and 19.) The reproduction takes place from the centre of the old joint, the 

 new formed ones having in their centre the perforation, and as yet appearing 

 very weak. This is a new proof that this perforation serves as a passage to the 

 nourishing vessel, and not a nerve, as many authors have, I believe, suggested. 



The PELVIS. (PL. n. fig. 9.) On the first columnar joints rests the pelvis, 

 formed of five nearly cuneiform joints having articulating surfaces probably 

 resembling those of the encrinite. Their five points meet near the alimentary 

 canal, they have each a central ridge above, and as the lower part of their exterior 

 circumference slopes downward to the salient angles of the column, they as- 

 sume externally a leaf-like appearance. 



The FIRST COSTAL JOINTS. (PL. n. fig. 9.) In the five concave spaces 

 formed by the five joints of the pelvis, the first costals are inserted. They slope 

 at the inner truncated edge, thus forming a saucer-shaped cavity leading to 

 the alimentary canal: they have two (although less conspicuous) bevelled and 

 slightly plicated muscular lip-like processes; the central excavation of these, 

 leading to the perforated transverse subtriangular ridge in the concave space at 

 their superior surface, which has a slanting direction downwards toward the 

 exterior, and serves for the insertion of the second costal joint. The exterior 

 circumference is 1 limited in the upper part, as far as the costals adhere laterally 

 to each other, having on the inferior part a process which projects for a short 

 distance into the space between the angles of the column, and has a semi-conical 

 figure. 



The SECOND COSTAL JOINTS. (PL, n. fig. 9.) The figure of these joints is 

 that of a horse-shoe, having in the interior an excavated truncated termination. 

 The exterior circumference is semicircular, and their lateral edges do not ad- 

 here to each othtr, but are united by the integuments cohering the abdominal 

 cavity. 



The SCAPULAE (PL. n. fig. 9) rest on the second costal joints, are of a 

 horse-shoe figure, and adhere laterally to each other only by the integument 

 mentioned above. At the superior surlace, a central ridge extends with a 



