BRACHIOPODA. 



31 



Thomas Davidson and William King,* and though fifteen years have now 

 elapsed since the date of its publication, later observations have hitherto added 

 comparatively very little to the results achieved by these eminent investigators, 

 and have taken nothing away from their value. The scope of this work in- 

 cluded not only a detailed discussion of the characters and relations of the 

 family, involving the establishment of an elaborate anatomical nomenclature, 

 but also descriptions of all the species then known to represent the three genera, 

 Trimerella, Monomerella and Dinobolus. This nomenclature we have adopted 

 without essential modification, and its application is sufficiently explained by 

 the accompanying 

 outlines, showing 

 the internal feat- 

 ures of Trimerella, 

 taken from the same " 

 work. We have 

 also accorded recog- 

 nition to the generic 

 term Rhinobolus, 

 which was made a 

 synonym for Trim- 

 erella in that work, 

 but we now possess 

 a considerably in- 

 creased knowledge 

 of this form, and 

 have elsewhere 

 quoted a subse- 

 quently expressed 

 opinion of Mr. Davidson's, abandoning his earlier views on the value of this 



Fig. 15. Pedicle-valTe of Trimerella. 



a, fleltidiuni. 



b, deltidial slope. 



c, deltidial ridges. 



d, areal borders. 



e, cardinal callosities. 

 /, cardinal facet. 

 g, lozenge. 

 A, cardinal buttress. 

 i, umljoiial ciiambers. 

 j, i)Iatforni. 

 /j, platform vaults. 

 I. median plate. 

 m, median scars. 

 n, anterior scars, 

 o, lateral scars. 

 p, post-median scars. 

 q, crown 1 



r, side > crescent. 



s, end ) 



t. transverse scars. 



u, archlet (vascular sinuses) 



w, sub-cardinal scars. 



X, umbo-lateral scars. 



Fig. 16. Brachial valve of Trimerella. 

 After Davidson and King. 



e, cardinal sockets. 



i, platlorm. 



/j, platform vaults. 



I, median plate. 



m, median scars. 



n, anterior scars. 



o, lateral scars. 



p, post-median scars. 



Qy crown 1 



r, side [ crescent. 



5, end ) 



t, trans\ erse scars. 



M, arclilet (vascular sinuses). 



V, cardinal scars. 



w, sub-cardinal scars. 



* On the Trimerellidfe, a Palaeozoic Family of the Palliobranchs oi- Brachiopoda. By Thomas David- 

 son, Esq., F. R. S., P. a. S., etc., and Professor William King, Sc. D. Honoris Causa, Queen's University in 

 Ireland: Quart. Journ. Geol. Soc, vol. xxx, pp. 124-173, pis. xii-xix. 1874. 



