116 SUPPLEMENT TO THE 



15. Atrtpa? Mawii, Dav. Sil. Sup., PI. IV, figs. 6, 6 a, 6 3, 6 c. 



Meeistella? or Atrypa Mawii, Da». Geol. Mag., New Series, vol. viii, p. 149, pi. v, 



fig. 5, 1881. 



Shell almost circular, as wide as long ; valves moderately convex ; ventral valve rather 

 the deepest ; no fold nor sinus, but a slight longitudinal groove divides the dorsal valve into 

 two equal lobes ; beak not much produced, with a small circular foramen. Surface of 

 valves marked at intervals by a few slightly projecting concentric ridges. 

 Length 6, breadth 6, depth 3 lines. 



Obs. — A single specimen of this shell was found by Mr. Maw among the debris from 

 the old Wenlock quarries at Benthall Edge in Shropshire. It is not possible to deter- 

 mine to what genus the shell should be referred, as its internal characters have not been 

 ascertained, and it was not considered right to sacrifice the only specimen known in an 

 attempt to discover the characters of its spiral appendages. Externally the shell is well 

 characterised, and it is with much pleasure I name it after Mr. Maw its discoverer. 



Genus — Glassia, Dav., 1881. 



16. Glassia obovata. Sow., sp. Sil. Mon., PL XII, fig. 19, and PI. XIII, fig. 5 ; and 



Sil. Sup., PL VII, figs. 11 to 20. 



Atbypa obovata, Sow. Sil. Syst., pi. viii, fig. 9, 1839. 



Glassia — Bav. Geol. Mag., New Series, vol. viii, January, 1881. 



At p. 121 of my ' Silurian Monograph ' I, described the exterior and the interior of the 

 ventral valve of this species with Sowerby's name Atrypa obovata, remarking at the same 

 time that all my efforts to obtain a sight into the interior of the dorsal valve had proved 

 unsuccessful, although I felt almost certain that the shell was provided with spiral 

 lamellae. 



While sorting some of the Brachiopoda obtained by Mr. Maw from the washings of 

 some seven tons weight of Lower-AVenlock " Buildwas Shales," ]\Ir. Glass observed 

 amongst them a few specimens of a circular, smooth Brachiopod, resembling in 

 shape Sowerby's Atrypa obovata, and at once began to operate upon them. To his 

 surprise he found that the shell was provided with spirals, but completely different in 



