136 CARBOXIFEROTJS CEPHALOPODA OF IRELAXD. 



1850. Aganides fasciculatus, A. d'Orbigny. Prod, de Paleont. stratigr., vol. i. 



p. 116. 

 1852. Ammonites Listeri (pars), C. G. Giehel. Fauna der Yorwelt, vol. iii, 



p. 476. 

 1854. GoxiATiTEs FURCATUS, J. Morrig. Cat. Brit. Foss., 2nd ed., p. 303. 



— — FASCICULATUS, J. Morris. Cat. Brit. Foss., 2nd ed., p. 303. 

 1855-57. Temnocheilus furcatfs, /. Kelly. Joum. Geol. Soc. Dublin, vol. vii, 



p. 8. 

 — Goniatites fasciculatus, /. KeUy. Joum. Geol. Soc. Dublin, vol. vii, 



p. 7. 

 1888. Gastrioceras fasciculatum, 31. Tzirelaer. Mem. Com. geol. St. Peters- 



bourg, vol. V, No. 3, p. 1. 

 1897. Pericyclus furcatus, A. H. Foord and G. C. Grid-. Cat. Foss. Cepli. 



British Museum, pt. 3, p. 149, 

 fig. 71- 



— — fasciculatus, a. H. Foord and G. C. Cricl-. Cat. Foss. Ceph. 



British Museum, pt. 3, p. 148. 

 [Not 1841. Goniatites furcatus, G. Miinster, Beitr. zur Petrefattenkunde, iv, p. 128, pi. xiv. 

 fig. 11.] 



Description. — Shell discoidal, somewhat inflated, umbilicated ; greatest thick- 

 ness at the umbilical margin, where it is two-thirds of the diameter of the shell ; 

 height of outer whorl two-fifths of the diameter of the shell. "WTiorls not fewer 

 than five (exact number not ascertainable); inclusion about one-half; umbilicus 

 somewhat less than one-half of the diameter in width, with subangular mai'gin, 

 deep, partly exposing the inner whorls. "Wliorl reniform in section, about twice as 

 wide as high, not much indented by the preceding whorl ; periphery broadly 

 convex, continuous with the convex sides ; inner margin ratliev Avide, well defined, 

 very steep. 



Body-chamber occupying at least one whorl ; aperture not seen. Chambers of 

 moderate depth ; snture-line as in PI. XXXYII, fig. G. Test ornamented with 

 strong, rounded, transverse ribs, which generally begin to bifurcate at or near the 

 umbilical margin, the bifiu'cation in some specimens not taking place till the 

 middle of the sides is reached. The ribs form a broad, shallow sinus in crossing 

 the periphery, the sinus sometimes becoming sharply concave in the median line ; 

 the intervening concave spaces wider than the ril)s. Covering the ribbing and 

 interspaces there are a series of very distinct, sharp, raised lines, disposed 

 irregularly as regards their distance apart ; on the ribs about two of the lines 

 occupy the space of 1 mm., but between them the lines are a little more spread 

 out. The tendency of these fine ribs to form bundles is well marked, and made 

 the name " fasciculatus," given by M'Coy to the specimen bearing the test, 

 singularly appropriate. 



AjUnities. — Though at first sight there is much resemblance between i'. 

 fascicuhifus and P. finiafn.^, yet on a closer inspection it is seen that the differences 



