POTERIOCERAS. 37 



the stone is so covered with cracks and inequalities that anything in the nature 

 of sutures is most diflScult to trace. Lastly, several of the nodes on one side are 

 removed by clean-cut concavities in such a way as almost to suggest that it had 

 agglutinated foreign substances after the manner of PJiiloxene. 



The species has been quoted in catalogues under the name of Porcellia 

 Symondsii in accordance with the old label which the fossil bore in the Museum. 

 Repeated examinations, however, convinced me that it was impossible that it 

 could belong to that genus. Being struck with its great likeness to a Cephalopod, 

 I then consulted Mr. Crick upon the subject, and his practised eye succeeded in 

 tracing several of the suture-lines, and thus settling not only its order but its 

 genus. This at once elucidated several of the perplexities about the fossil. It 

 became evident that its elliptic shape was wholly due to pressure, and also that 

 the same cause had probably exaggerated the originally broad, gently concave 

 ventral surface into a narrow and deeply concave groove. Further, on our 

 examining the specimen figured by Phillips ^ as Nautilus tetragonus {=: Biscites 

 Omalianus, de Koninck,^ sp., according to Foord^), which Hyatt refers to 

 Suhclymenia, it was seen that the surface-ornament, though not identical, was 

 of such a kindred nature as to confirm Mr. Crick's conclusion. 



Affinities. — Our species is at once distinguished from the type species of the 

 genus, S. evoluta, Phillips, sp.,* with which de Koninck ^ afterwards identified his 

 Nautilus Omalianus, by the presence of nodes. 



II. Family — Gomphoceeatidj;, Pictet, 1854. 

 1. Genus. — Potbeioceeas, M'Coy, 1844. 

 1. Potbeioceeas ? sp. Plate IV, figs. 3, 3 a. 



Description. — Shell apparently short, very rapidly tapering, recurved. Section 

 quadrately sub-ovate, wider than deep. Siphuncle small, circular, 1 mm. in 

 diameter, sub-central, being rather near to the convex side. Body-chamber 

 expanding. Septate part apparently rapidly expanding, consisting of very narrow 

 chambers, 3 mm. in height, with rather shallow concave septa, rather oblique, 

 sloping slightly down (?) toward the convex side. Test thin. 



Size of fragmentary specimen : height 40 mm. ; transverse diameters 26 mm. 

 and 30 mm. 



' 1836, Phillips, ' Geol. Yorks.,' vol. ii, p. 233, pi. xvii, fig. 2i; and pi. xxii, figs. 33, 34. . 



2 1851, de Koninck, 'Desc. Anim. Foss. Terr. Carb. Belg.,' Suppt., p. 61, pi. k, fig. 3. 



3 1891, Foord, ' Catal. Foss. Cephal. Brit. Mus.,' pt. 2, p. 87. 



* 1886, Phillips, ' Geol. Yorks.,' vol. ii, p. 237, pi. xx, figs. 65—68. 



5 1880, de Koninck, ' Ann. Mus. Eoy. H. N. Belg.,' vol. v, pt. 2, p. 83, pi. xlv, figs. 5—6 a. 



