INVERTEBRATES. 213 



up between the brachial pieces and connect with the vault. 

 The first anal plate is about as large as the first radials, as long 

 as wide, heptagonal in form, and surmounted by three smaller 

 hexagonal pieces in the second range, the middle one of which 

 projects above the others. Surmounting these, there are three 

 pieces in the third range, the two lateral of which each sup- 

 ports an irregular piece above, while the middle one projects 

 considerably above the others, in a wedge-shaped point, and 

 bears on its superior sloping sides a series of protuberant 

 pieces surrounding the small anal aperture, which opens later- 

 ally a little above the horizon of the arm openings. 



The summit is depressed and composed of unequal, irregu- 

 lar pieces, one of which over each of the rays, and another near 

 the middle, are usually larger than the others, and appears 

 to have been tumid, or may even have been extended into 

 short spines, so as to place it in Dorycrinus, if that name is to 

 be retained for a section of this genus. Height to top of vault, 

 0.59 inch; breadth across the summit between the groups of 

 arms, about 0.60 inch ; do. from the arm openings on opposite 

 sides, 0.73 inch. 



This species bears some resemblance to A. \_Amphoracrinus] trinodus, of 

 Hall, but has the base less truncated, the vault more flattened on top, and pro- 

 vided with six nodes or spines, instead of three; while it has four arms instead 

 of three to each posterior ray, and four instead of two in the anterior. Its 



most marked characters are its short, obconical, or 

 Fig. 15. 



turbinate form below the arms, and truncated dome. 



vvOO The latter rises somewhat abruptly above the arms, 



<^X? ty~~}n3 r^ C§> as mucn as about one-third of the height of the 



OC'/y/^^^^y^^f^' CU P below these, but is abruptly flattened on top, so 



s^-'vC-^K-Z/nfir' as ^° 8^ ve ^ a truncated appearance. Our specimen 



is not in a condition to enable us to determine 



"jAiis} /-, /""") ^~ y &]Qr& whether or not the summit had spines, though some 



Q C} O r4 o^ remains of the larger piece over each ray, seem to 



\/ indicate that they were, when entire, quite promi- 



Aetinocrinus subtwrUnatus. nent. The sinuosities between the rays gives the 



(Near natural size.) b()dy & pentalobate outline ag geea from below . 



Locality and position : Same as preceding. 



