Maryland Geological Survey 235 



Occurrence. — ^Heldekijerg Formatiox, Keyser Member. Keyser, 

 West Virginia. 



Colleciion. — U. S. National ^Museum. 



Jaekelocystis avellana Schuchert 

 Plate XXXIII, Figs. 3, 4 



Jaekelocystis avellana Schuchert, 1904, Smith. Misc. Col., vol. xlvii, pt. ii, 

 No. 1482, p. 226, pi. xxxvii, figs. 11, 12; text fig. 28. 



Description. — Theca shaioed like a hazelnut, the resemblance suggest- 

 ing the name, about 10 mm. in length and breadth, in the largest of three 

 known examples. Plates nearly smooth ; for their individual form, see 

 the diagram (fig. 8) and pi. x.xxiii, figs. 3, 4. 



Fw. S. — Analysis of Jaekelocystis avellana Schuchert. 



Ambulacra narrow, but appearing wide on account of their lying in 

 rather deeply excavated thecal grooves, with sharply elevated margins, 

 extending to the lower ends of the second or to the top of the basal circle 

 of thecal plates. The 4 ambulacra are regularly disposed and do not con- 

 verge. Nature of brachioles unknown, about 26 on each ambulacrum, or 

 13 on each side. Ambulacrals thick, causing the ambulacral furrow to be 

 narrow ; ambulacralia not preserved. Hydropore conspicuous and situated 

 as in J. liartleyi. Anal pyramid not preserved. Anal area less con- 

 spicuous, but otherwi?e as in J. hartJei/i. Pectiuirhombs as in the species 

 just cited, with 1 or 2 dichopores less to each rhomb. Column unknown. 



Occurrence. — 'Helderberg Formation, Keyser Member. Keyser, 

 West Virginia. 



Colleciion. — TJ. S. National Museum. 



