138 PROCEEDINGS OF THE ACADEMY OP 



to each ray, excepting sometimes in the anterior ray. Second radial pieces 

 generally contracted in the middle, and usually separated from the first radials 

 by gaping sutures. Arms generally shorter and sometimes simple, often with 

 the pieces so arranged as to present a zigzag appearance. Body short and 

 rounded or concave below, or varying to an inverse bell shape or obconic 

 outline.* Anal pieces sometimes with only a single one included as a part of 

 the wall of the body. 



Includes S. simplex (the type), S, spinobrachiatus, S. iortuosus, S. doris, S. 

 seqnalis, S. carinatus, S. dichotomus, S. dactyliformis, S- divaricatus, S. Jlalli, S. 

 nodohrachiatus, S. lyriope^ S. orbicularis, S. ramosus, S. robusivs, S. subcarinatus, 

 S. subtortuosus, S. uncus, and S. Whitei, Hall, as well as his Cyathocrinus macro- 

 pleurus. Also S. longidactylus, McChesney and S. decadactylus, S. macrodactyhis, 

 S. solidus, S. Wachsvmthi, S. Clio, S. Thetys, S. nanus, S. delicatus, S. penicilhis, 

 S. fiscellus, S. scalaris, S.Juvenis, S. rudis, S. liUiformis,-\ and S. noiabilis, M. and 

 W. 



Poteriocriniles dactyloides, P. latifrons, of Austin, and P. te?iuis, of Miller, 

 would also fall into this section, giving it the limits usually admitted. 

 3. — Subgenus Zeacrinus, Troost. 



Differs from Scaphiocrinus in having the body more generally rounded and 

 concave below, and always with more than one anal piece included as a part 

 of the walls of the bod}'. Also in having the arms generallj' more frequently 

 bifurcating and the inner divisions all simple, as well as in having the free 

 radials generally wider. 



Includes -^. ma^?«oZ/(T/br?«M, Troost ; Z. elegans, Z. ramosus, Z. paternus, Z. 

 intermedins, Z. scoparius, and Z. Worlheni, Hall ; Z. bifurcatus, McChesney ; Z. 

 ovalis, Lyon and Cassiday ; Z. spi)iosus, Owen and Shumard ; and Z. discus, Z. 

 Troostanus, Z. scohina, Z. asper, and Z. lyra, M. and W. Also Z. perangulatus 

 and Z. sacculus. White. 

 4. — Subgenus C(eliocrinus, White. 



Differs from Scaphiocrinus in having the ventral prolongation much inflated or 

 balloon shaped, instead of nearly cylindrical. 



Includes Poteriocrinus dilatatus, and P. ventricosus, Hall. 



POTERIOCRINITES? PERPLEXCS, M. and W. 



Body small, somewhat cup shaped, with sides a little expanding above and 

 rounding to the column below; height to top of first radial pieces more than 

 half the breadth at the same point. Base small, much depressed, or nearly 

 flat, with a pentagonal outline. Subradial pieces each nearly as large as the 

 whole base, about as wide as long, three hexagonal and two heptagonal 

 (counting a very obtuse angle at the middle of the base of each). First radi- 

 als nearlj' twice as large as the subradial pieces, and proportionally wider, 

 pentagonal in form, and each with a moderately deep rounded sinus, rather 

 more than half the breadth of its upper margin, for the reception of the suc- 



* It is worthy of note that the original tj'pical species of Scaphincrinus {S. simplex. Hall), 

 has its body much depressed and rounded, but not concave, below, with but one anal 

 piece only, included as part of the walls of the body. It also has but two radials to each 

 ray, with all the arms simple, and two from each ray, excepting in the anterior ray, which 

 supports only one arm. [This species is wrongly described, and illustrated by the cut, 

 in the text of the Iowa Report, part ii, vol. 1, p. 550 — 52, as having the arms double from 

 their origin on the second radials all around, there being but one arm in the anterior ray 

 in the type specimen now before us.] The group, however, has been extended by ProV. 

 Hall and others, so as to include species presenting all the characters given above, and 

 might be divided into several sections distinguislied from each other and from the typi- 

 cal form, on quite as good characters as those distinguishing the latter from Zfacritms. 



t This is our Poteriocrinus carinatus, (Illinois Report, vol. iii, pi. 17, fig. 1). As Prof. Hall 

 had previously used the name carinatus for a Scaphiocrinus, it becomes necessary to give 

 our species a new name. At the time we referred it to Poteriocrinites proper we were not 

 aware that tliere is a little group of species having the other characters of Scaphiocrinus, 

 and yet with three radial pieces to each ray. 



[July, 



