26 SUPPLEMENT TO THE 



manner in a specimen sent to him by Mr. Whidborne from Hope's Nose, near Torquay : 

 of these we give two figures on PL I of this Supplement. These figs. 10, 10a, 

 require no detailed explanation, as that will be found under the description of Athyris 

 in the accompanying Silurian Supplement. In its hook-shaped attachments to the hinge- 

 plate, and in the character of its loop, with its roof-shaped projection, curved lamella, and 

 accessory lamellae, this species is clearly shown to be of the true Athyris type. 



In my ' Permian and Carboniferous Monograph ' I published a full description, with 

 figures, of the spirals and their connections in A. pectinifera and A. amhiyua, and now, 

 as recorded in these Supplements, the complete arrangement of the spirals and their con- 

 nections have been worked out by Mr. Glass in A. concenfrica, A. piano- sulcata, A. 

 amhigua, and A. spiriferoicles, and all have been described and figured as correctly as was 

 possible. The descriptions and figures will show that the spirals, loops, and attachments 

 are esentially the same in all species of a same genus, although they may differ a little in 

 minor details. 



13. Athyris rugata, Dav. Dav., Dev. Sup., PI. I, figs. 25, 25f/, 



Shell small, almost circular or as broad as long. Valves convex, with a slight mesial 

 elevation or fold near the front in the dorsal valve, and a small concave sinus in the ventral 

 one; beak small, incurved; foramen minute. Valves covered with a small number of 

 strong irregular concentric ridges. Interior not known. 

 Length 4, width 4, depth 1 line. 



I know very little about this shell, having seen only two specimens of it. Mr. 

 Whidborne is of opinion that it is a distinct species ; and its few comparatively very strong 

 concentric ridges seem to distinguish it from A. concenfrica. 



It occurs in the Middle Devonian at Hope's Nose, near Torquay. 



