149 PALEONTOLOGY OF NEW-YORK. 



Arms composed at base of two thick plates, succeeded by about four 

 wedgcform plates ; and above this an alternating series of interlocking 

 plates, which are furnished on their outer margins with jointed ten- 

 tacula. Tentacula undetermined. 



Column large, consisting of alternating thicker and thinner joints. 



This beautiful species is figured and described from a mould in sandstone, and 

 from detached j)latcs and fragments of columns. It belongs to the type having simple 

 arms like JVf. plumosus and M. spinulosus, and is the finest species of the group. 

 There is some obscurity in structure about the bases of the arms, but the representa- 

 tion is essentially correct. Each third radial supports two first brachial plates, and 

 these each in turn two others, from which originate the simple arms; giving twenty- 

 arms, as in the other species of this group. Tlie portions of the aims remaining are 

 more than three times as long as the body, and probably they were originally at 

 least four times as long as the body. 



Fig. 1. The specimen, natural size, preserving the body, and on one side a part of the arms 

 and a portion of the column. 



Fig. 1 a. Diagram illustrating the structure from the base to the lower part of the arms (for 

 comparison with structure of Mariacrinus packydaclylus and M. ■plumosus, plate 

 iii). 



Fig. 2 & 8. Fragments of columns apparently of this species. 



Fig. 4. Section of column fig. 3. 



Geological position and locality. In the Oriskany sandstone : Cumberland, Md. 



Mariacrinus (Subgenus) Tectmocrinus striatiis (n. s.). 



Plate LXXXYI. Fio. 12 & 5 - 11. 



Body unknown. Surface of plates marked by strong elevated striae, di- 

 verging from the centre. Basal plates four, Avider than long, small. First 

 radial plates wider than high. 



Column small. 



This species is founded on the base and first radial plates, and numerous separated 

 plates of the same character. The surface markings are not unlike those of Techno- 

 crinus andrewsi, but are finer, the column and base proportionally much smaller, 

 and the first radial plates proportionally shorter. 



Fig. 12. The basal plates anchylosod together with a small portion of the column attached, 

 and also one first radial plate. 



Fig. 5, 6, 7, 9, 10 & 11. Several plates of different series belonging to this species. 

 Geological position and locality. In the Oriskany sandstone : Cumberland, Md. 



