100 DEVONIAN FAUNA. 



shell. Section roughly quadrilateral, the dorsal face being slightly convex, the 

 two sides oblique, and the ventral face very wide and slightly convex, the ventro- 

 dorsal being to the transverse diameter in the ratio of 2 : 3. Junction of the 

 sides with the ventral face marked by a row of very large, regular, distant, and 

 bluntly conical nodes or horns, set perpendicularly to the median plane. 

 Traces of blunt ridges upon the sides, starting from these tubercles and sweeping 

 upwards over the sides and then arching round suddenly so as to become 

 transverse upon the dorsal surface. Chambers concave. Surface covered by 

 numerous fine, regular, slightly undulating, longitudinal lines or threads upon 

 sides and dorsal face. 



Size. — Length 85 mm. ; width of whorl 44 mm. ; ventro-dorsal diameter, near 

 mouth, about 30 mm. 



Locality. — "Wolborough. There are two specimens in the Museum of Practical 

 Geology, one of which is Phillips's type, and two in the British Museum. 



Remarks. — None of the specimens are perfect. The surfaces of all except 

 one are decayed after the manner of so many of the Wolborough fossils, so 

 that the finer markings of the surface cannot be made out. Phillips's type- 

 specimen differs in some respects from his figure, being slightly smaller, having a 

 sharper inferior bend and bearing more acute tubercles. It has been broken and 

 injured since it was drawn in Mr. Godwin- Austen's Collection; but there is no 

 doubt of its identity, for not only does the position of the encrusting matrix agree, 

 but there are two specimens of Davidsonia Verneuili upon its back, which Phillips 

 has represented in their correct positions, but did not otherwise allude to or 

 describe. It is interesting to observe that two of Mr. Vicary's specimens of the 

 kindred G. prseclarum have these rare parasitic brachiopods upon their surface. 

 The texture of the shell seems to have been thick in some parts and very thin 

 in others. 



The best preserved specimen in the British Museum had been identified by 

 Mr. Foord with G. ornatum, d'Arch. and de Vern., but after comparing it in his 

 company with Phillips's type we came to the conclusion that it agreed perfectly 

 with that, and was distinct both from G. ornatum, of Goldfuss and the G. ornatum 

 of Phillips. We also concluded that the very poor specimen which was figured 

 and named G. nautiloideum by Phillips, and which is the second of the two 

 specimens in the British Museum, must be regarded as in all probability a specimen 

 of this shell. It is a very much worn cast, and is only distinguishable from the 

 other shells by the general (not entire) absence of nodes, and by its more regular 

 section. These differences may, however, be fully accounted for by the great 

 amount of surface-decay which it has undergone, if not also by such specific 

 variation as we have already observed in G. prseclarum,. 



