36 



radials, and upon each proximal side a single tertiary radial, which 

 gives to each of these rays four arms. In the right lateral ray, 

 the third primary radial supports, on one side, two secondary 

 radials the last being axillary and supporting on the outer side 

 two tertiary radials and on the inner side only one; and on the 

 other side a single secondary radial, which supports, on the distal 

 side, three tertiary radials, and, on the proximal side two, which 

 gives to this ray four arms. In the ray on the right of the 

 azygous area, the third primary radial supports, on the side adjoin- 

 ing the azygous area, two secondary radials, the last being axillary 

 and supporting on each upper sloping side a single tertiary radial ; 

 and on the side distant from the azygous area three secondary 

 radials, but two of these are upon the proximal sloping side of 

 the first, and, upon the superior side of the first, there is an inter- 

 secondary plate, while the distal side abuts the first tertiary radial, 

 in the adjoining ray. This is the structure of the specimen 

 illustrated and gives to this* ray only three arms, but, we think 

 this structure is abnormal, because this intersecondary plate is in 

 the position of a tertiary radial and because there is a plate out 

 of place at the top of the azygous area that we will again call at- 

 tention to. Beside, we have another specimen belonging to this 

 species, that happens to be injured so as not to disclose the whole 

 structure of the ray, but there are four ambulacral openings, and, 

 so far as preserved, the ray is like the one on the left of the 

 azygous area. There are, therefore, in the specimen illustrated, 

 only seventeen arms, but we believe, from the structure and 

 evidences above mentioned, that one of the rays has suffered from 

 an injury that produced an abnormal ray and that the species bears 

 eighteen arms, and that the true arm formula is 4+4+2+4+4, 

 instead of 3+4+2+4-1-4. We do not wish to be understood, how- 

 ever, as intimating that seventeen ambulacral openings to the vault, 

 is an abnormal condition of a crinoid, on the contrary, seventeen 

 may as well be normal as eighteen or any other number. It is 

 the peculiar intersecondary plate and the peculiar plate at the top 

 of the azygous area and the evidence afforded by another injured 

 specimen, that lead us to think the specimen illustrated is abnor- 

 mal. If the ray was an ordinary three-armed ray, we would say 

 the specimen is normal and the species has only seventeen arms, 

 and, if another specimen constructed, on the same plan, was found 



