GONIATITES. 65 



Description. — Shell discoidal, almost completely involute, more or less deep, 

 with five or more whorls. Whorls increasing very slowly, the mouth being more 

 than half-filled by the back of the next whorl. Sides flat and parallel for the 

 greatest part of their diameters, then arching round in a bold curve to the back, 

 which is nearly flat and very broad, and is sometimes defined by slight lateral 

 excavations. Umbilicus about one fourth the diameter of the shell, very deep and 

 trochiform, lined by a convex spiral ridge formed by the margins of the successive 

 whorls. Suture-line with a broad blunt central lobe, smaller subtriangular central 

 saddles and lateral lobes, and slightly concave lateral saddles. 



Size. — Phillips's original specimen measures 50 mm. in height, 38 mm. in width, 

 and 15 mm. in depth ; another specimen measures 35 mm. in height, and 13 mm. 

 in depth. 



Locality. — Wolborough. Phillips's Devonian type-specimen is in the Lee Col- 

 lection, now in the British Museum. There is a second specimen in the same 

 Museum which is fractured so as to show the suture-line. There are four smaller 

 shells in Mr. Vicary's Collection which were labelled G. excavatus by Salter, but 

 some of which are not very typical. In the Torquay Museum (Battersby Coll.) are 

 three specimens, one of which is very small but presents all the characters of the 

 species. There are five specimens in the Museum of Practical Geology. 



Remarks. — A comparison of the type-specimens in the British Museum shows 

 most clearly that this species is quite distinct from the Yorkshire shell described 

 under the same name by Phillips.^ In that the section through the shell is almost 

 ovoid, the back is narrow and deeply convex, the whorls increase very rapidly, the 

 umbilicus is differently formed, and sulci are generally present. It is probable 

 that Phillips himself did not intend to unite them, though giving them the same 

 name, as he does not quote the ' Geology of Yorkshire ' in his description in the 

 ' Palaeozoic Fossils.' Hence, as it was given first to the Carboniferous fossil it 

 cannot be retained for the present species. Mr. Lee's original specimen, on the 

 whole, agrees fairly well with Phillips's figure of it, but it is broader, and the whorls 

 increase less rapidly [i. e. the mouth is shorter) than there represented, and in 

 these respects it comes nearer to the generality of the Devonshire specimens. The 

 species appears to have been rather variable, and the question which Phillips 

 raised, as to the possibility of its being identical with the shell which he referred 

 to G. glohosus, Munster, is therefore not very easy to solve. Typical specimens 

 of each are very different in shape, but some of the deeper forms of G. molar'ms 

 approach very near to the specific confines of G. glohosus. Their depth in 

 some instances amounts to half the width. The excavation on each side of the 

 back also seems sometimes almost invisible. But on the other hand, the sugges- 

 tion that it may be the adult form of Mimster's shell does not seem borne 



1 1839, Phillips, « Geol. Yorks.,' vol. ii, p. 235, pi. xix, iigs. 33, 35. 



