FOSSILS OF THE BURLINGTON GROUP. 353 



quite in to the body, while even the interbrachial sinuses 

 extend nearly in to the body. The column is of moderate 

 thickness near the base, where it is round and composed of 

 tli in pieces with sharp projecting edges, pierced by a nearly 

 round central canal. 



Hight to horizon of arms, 0.73 inch; breadth across at 

 the interradial sinuses, 0.90 inch; hight of vault, 0.46 inch. 



This species has its plates sculptured in nearly the same way, and 

 presenting much the same roughened appearance seen in 8. glyptus, 

 Hall (sp.), but it differs materially from that and all of the other species 

 known to us, that resemble it in other respects, in having deep inter- 

 radial and aual sinuses in its disc, as in the subgeuus Physetocrinus, 

 with which it also appears to agree in its ventricose vault. It is the 

 only species known to us, however, apparently belonging to that group 

 that lias its body so narrow and produced below, and its body plates 

 presenting this style of angular sculpturing. If the iuterradial and 

 anal sinuses of its disc were filled with intercalated pieces it would pre- 

 sent nearly all the characters of a typical Strotoerinus. Consequently, 

 it may be regarded as a connecting link between these groups, and with 

 a few others shows that they cannot be properly separated more than 

 subgenerically. 



Locality and position Upper beds Burlington group of Lower Car- 

 boniferous, at Burlington, Iowa. No. 67 of Mr. WACHSMUTH'S collec- 

 tion. 



Section (6). 

 STROTOCRIXUS ECTYPUS, M. and W. 



PL 7. fig. 5. 

 Strotocrinu* tctypus. MEEK and WORTHKX. Proceed. Acad. Sat Sci., Phila., 1869, p. 139. 



BODY depressed, very rapidly expanding to the third ra- 

 dials, above which the secondary and tertiary radials and 

 brachial pieces curve out horizontally. Base about twice 

 and a-half as wide as high, truncated, slightly concave, 

 and not expanded or thickened below, but with small nodes 

 around the margin of the under side, placed one at the ter- 

 mination of each of the costa?. First radial pieces wider 

 than high, two heptagonal and three hexagonal. Second 



46 



