ibs 



is of an elliptical form, having the sides pressed in, but becomes round as the 

 arm elongates. The growth and insertion of the auxiliary side arms in the 

 column, is conformable to what was observed when speaking of Actinocrihites 

 triaconta dactylus. One specimen (fig. 8. and 9.) in my possession shows the 

 conical insertion of the first auxiliary arm joint very distinctly. 



The pelvis (PL. i. fig. 5. and 6.) is saucer-shaped, composed of three plates, 

 having in the depressed centre where they articulate to the column, a pentapeta- 

 lous opening forming the entrance to the alimentary canal. At the upper edge 

 they are excavated, forming five slightly concave spaces, showing a finely 

 striated rim at the exterior margin for the firmer articulation of five intercostal 

 plates. 



On account of the first INTERCOSTAL PLATES, which are of an oblong 

 square form, inclining outwards, an angle is formed between each two, into 

 which a first costal plate is inserted. . 



' i * 



The five FIRST COSTAL PLATES are heptagonal and pointed, supporting 

 each a hexagonal second costal plate, and a scapula. 



On the first intercostal plates (PL. i. fig. 2.) rest a series of several hex- 

 agonal oblong intercostal plates, gradually decreasing in size upwards, hav- 

 ing in the angles between them and the costals a few irregular intercostals, 

 placed in a double series on the sides where (as in the former species) the 

 structure of the animal occasions that wider interval between two of the arms 

 than between the rest, for the purpose of which we are yet unable to account. 

 The intercostals and irregular intercostals mix above with the mass of minute 

 plates belonging to the integument over the abdominal cavity. 



The ARMS and FINGERS. From each of the scapulae proceed two first arm 

 joints, and from these a second, between whose inner angles a clavicular plate 

 is inserted. C. STOKES, Esq. sent me a drawing of the superior portion 

 of this animal found at Dudley (PL. I. fig. 1.) which shows that the arms sup- 

 port two hands each provided with several fingers. 



A radiating contraction (PL. i. fig. 2.) is capable of being formed by mus- 

 cular action on each of the costal and intercostal plates, similar to that noticed 

 in Actinocrimtes Poly dactylus. A powerful contraction (fig. 3.) arising from 



