PERICYCLUS FASCICULATUS. 137 



far outweigh the resemblances. P. fi(natns is the more slowly tapering shell of 

 the two, and has more numerous whorls, giving a considerably larger umbilical area. 

 Again, though the ribs (at least in casts) are similar in character in the two species, 

 the bundles of finer ribbing in P. Jascicnlntus, only seen when the test is preserved, 

 are entirely absent in P.funatiis. The two species agree perfectly in the bifurca- 

 tion of the ribbing, and M'Coy, who seems to have relied upon Sowerby's 

 description, is not accurate when he states that the ribs in I'.fniiatns (he calls them 

 " ridges ") are " simple, equal, and proceed directly across the shell." Periodic 

 constrictions are present in both species. 



From P. multlcostatus, sp. nov. (p. 139), the present species can be easily dis- 

 tinguished by its less numerous and much coarser ribs and larger umbilicus, and 

 the same features distinguish it still more manifestly from i'. Dooliijlensix, which is 

 remarkable for the extreme fineness of its ribbing. 



lieinarJcs. — While looking over the choice collection of Carboniferous Limestone 

 fossils in the possession of ]\Ii\ Joseph Wright, of Belfast, found chiefly in Cork 

 and places in its vicinity, he drew my attention to a specimen of the so-called 

 Nautilus l^Perlcyclus^ furcatus from Blackrock, in which a portion of the test was 

 preserved, pointing out that the ornamentation was precisely that of the specimen 

 to which M'Coy gave the name" Goniatltes" fasclciihdus, in allusion to the bundles 

 of sharp raised lines or fine ribs covering the test.' Fortunately M'Coy's type is 

 still extant (PI. XXXVII, fig. 5), and a comparison of it with Mr. Wright's 

 specimen soon convinced me that that observer was quite correct in his view of 

 tlie identity of the two so-called species. In most specimens of P. fasciciilatus 

 collected the test is stripped off and remains in the parent rock, nothing but the 

 cast being left in the collector's hands. This explains M'Coy's omission to notice 

 the finer ribbing, since his specimen was doubtless a cast. It is imfortunately 

 missing from the " Griffith Collection" of the Dublin Museum, in which many of 

 M'Coy's type specimens are contained, but the excellent figure of it in the 

 ' Synopsis ' renders it easy of identification. 



Though aU the specimens of the present species known to me from Cork and 

 its vicinity are more or less distorted, some excessively so, those from other parts 

 of Ireland are of the normal shape. One of these, collected by myself in the Claue 

 quarries, was figured in the ' Catalogue of Fossil Cephalopoda, British Museum,' 

 Part 3, and shows the natural form. It is refigured in the present work 

 (PI. XXXVII, fig. 2), and may be compared with the larger individual represented 

 on the same plate (fig. 3) . Owing to the crushing the latter has Ijeen subjected to, 

 its true shape is altered, and the lateral view (fig. 3 a) shows some of the peripheral 



' This name must be retained to the exclusion oi fnrcaius (1) because it was the first to bo 

 described in the ' Synopsis,' and (2) because it shows the ornaments on the test, whereas the neimw 

 furcatus was applied merely to the cast of the shell. 



