]\Iai!Yla.\i) Geol()(!Tc'al Survey ' 233 



Genus JAEKELOCYSTIS Scluicbert 



Jaekelocystis haktleyi Schuchert 



Plate XXXII, Figs. 12-16 



Jaekelocystis hartleyi Schuchert, 1903, Amer. Geol., vol. xxxii, p. 231. 

 Jaekelocystis hartleyi Schuchert, 1904, Smith. Misc. Col., vol. xlvii, pt. ii, No. 

 1482, pp. 224, 225; pi. xxxvii. figs. 4-8; text fig. 27. 



Description. — Ambulacra narrow, excavated into, and but slightly ele- 

 vated above, the theca, and in normal specimens extending to the column. 

 Each pair of ambulacra, or E. I and E IT, E lA^, and R V, converging and 

 almost touching each other near the column. In one individual R I is 

 but half the normal length and R II is almost aborted, having but 6 

 brachioles. In another individual R I is entirely undeveloped, while in a 

 third specimen R II is absent. In a fourth specimen R V is forked, the 

 branch developing on the left. In full-grown specimens, there are about 

 34 brachioles to each ambulacrum, 17 on either side. Brachioles stout 

 and folded over each other medially ; length unknown but apparently quite 

 short. Ambulacral grooves narrow and shallow, with very minute am- 

 bulacralia. 



Dichopores on plates 1, 1?, and 14 not shown at the surface, being deeply 

 situated within small oval pits, each with a rim highly elevated above the 

 surface of these plates. Those on plates 5, 18, and 15 show the dichopores 

 with the excavation deepest orally, and are here delimited by a crescentic 

 lip. About 8 folds in each rhomb. 



Hydropore conspicuous, situated on a small piece placed above and 

 between plates 18 and 13. No madreporite discernible. 



Anal pyramid small, not strongly elevated, composed of 6 pieces, but 

 made quite prominent by the protrusion of the bounding margins of thecal 

 plates 7, 8, 13, and 14. 



Column comparatively stout, and, as is usual in cystids, composed of 

 thick segments near the theca. Length unknown. 



This beautiful, regular, but small cystid is readily distinguished from 

 the other species of Jaekelocystis by the pyrifonn outline, strong sculptur- 

 ing, and the more prominent ambulacra. J. papilJata is also easily identi- 

 fied by the much finer papillose ornamentation. 



