138 SUPPLEMENT TO THE 



France (see ' Explication de la Carte Geologique de France,' Vol. 4, Atlas, pi. xv, figs. 1, 

 2). A specimen given to me by Mr. CEhlert is scarcely distinguishable from some of 

 the Dudley- Wenlock specimens. 



Very fine preparations of the spirals and their attachments, from the able hands of 

 Mr. Glass, will be found figured in PI. VI of this Supplement. Spirifers are not known 

 to exist in our Lower-Silurian and Cambrian Rocks, the solitary example of the Spiriferid 

 Cyrtia trapezoidalis excepted. They are also specifically few, but individuals abound in 

 the Upper-Silurian and especially in the Wenlock formation. 



A vast number of specimens of Spirifera pUcafeUa, var. radiata, var. interlineata, and 

 var. (jlohosa, Sj). sulcata, Sp. elevata, and 8p. crispa, were obtained by Mr. G. Maw from 

 the Wenlock Limestone and its shales in Shropshire.. Sp. crispa and Sp. elevata were 

 the most abundant forms. The only other British Silurian species of the genus, 8p. 

 hijuyata, M'Coy, has not been hitherto discovered in our English or Scottish rocks. 



The spirals of Sp. crispa have been developed by the Rev. N. Glass, and a figure 

 will be found in PI. IV of this Supplement. Sp. sulcata is a beautiful and finely 

 sculptured species, but apparently less abundant than the other forms above recorded. 



Genus — Merista, Suess, 1851. 



21. Merista? cymbula, Lav. Sil. Mon., PI. XXII, figs. 28, 29; Sup., PI. VIII, 



figs. 6 to 9. 



Since describing this species at p. 204 of my ' Silurian Monograph,' Mrs. R. Gray has 

 found larger and better preserved examples, as well as internal casts of the ventral 

 valve, in the Upper Caradoc at Thraive and Druramuck in the Girvan Valley, Ayrshire. 

 These Scottish specimens agree with those from the same formation that have been dis- 

 covered at Hindre-Wen, Cerrig-y-Druidion, and which we have already described and 

 illustrated. It has not, however, been possible to determine the genus to which this 

 small species should be referred, as we do not know whether it was provided or other- 

 wise with internal spiral supports. We leave it therefore provisionally Avith Merista, 

 from which it will probably have to be removed as soon as its interior characters shall 

 have been determined. None of our Scottish examples, collected by Mrs. R. Gray, 

 exceeded 4 lines in length by 3| lines in breadth. 



The shell is marginally either nearly circular or slightly longitudinally oval, broadest 

 and rounded anteriorly, tapering somewhat posteriorly ; hinge-line very obtusely angular, 

 and a little shorter than the breadth of the shell. Ventral valve deep and uniformly 

 convex, beak proportionately rather large and incurved, no area nor foramen observable; 

 dorsal valve slightly convex at its posterior lateral margins, concave along the middle and 

 anteriorly ; surface smooth. 



