﻿rtiynciionella 



07 



Terebbatula parallelipipeda, Bronn. Leth. Geog., p. 71 (non T. Wilsoni, var.) 

 Rhvnchonella — Sandberger. Die Brachiopodcn Itheinischen Schich- 



tensystems in Nassau, p. 43, pi. xxxiii, fig. 



12, 1852. 



Spec. Char. Shell of a nearly equilateral pentagonal shape, wider than long ; dorsal 

 valve moderately convex and divided into three lobes of almost equal width ; the central 

 lobe forms a well-marked, elevated, mesial fold, but at a short distance from the margin 

 the valve is suddenly bent down at right angles to meet the similarly bent margin of the 

 opposite one. Ventral valve less convex than the opposite one, with a deep mesial sinus 

 bounded by two angular ridges ; beak prominent but small, much incurved, and exhibiting 

 under its angular extremity a small circular foramen, surrounded by a deltidium. Surface 

 of each valve covered with a great number of fine radiating striae or ribs, which are split, 

 or grooved, in their proximity to the margin. 



Proportions very variable ; a well-shaped specimen measured — length 8, width 9^, 

 depth 5^ lines. 



Obs. Some difference of opinion appears to exist with reference to the name this 

 species should retain. Baron von Buch, Sowerby, and the generality of naturalists, have, 

 since 1834, made use of the term primipilaris for the Eifel and English Devonian shell. 

 At page 1247 of Bronn's 'Index Palaeontologicus' we find P. primipilaris, v. Buch, 

 considered a synonym of T. maryinalis, Dalman ; but on reading Von Buch's description of 

 T. primipilaris I find that he distinctly refers his type to the limestone of Gerolstein, in 

 the Eifel, and afterwards merely alludes to a specimen from Gothland, which in Schlotheim's 

 collection, so named, bears some resemblance to the Devonian species. Schlotheim's is 

 only a catalogue name, and consequently cannot claim priority over Von Buch's, since the 

 last palaeontologist has both figured and described his species, which Schlotheim has not 

 done. I am therefore of opinion that the term primipilaris should be made use of in the 

 sense proposed by Von Buch, Sowerby, and others. Rh. primipilaris is a very remarkable 

 species, and so variable that several so-termed species have evidently been fabricated out 

 of some of its variations in shape, and we will now allude to the principal ones which 

 occur in Great Britain. 



The typical form, that agreeing with Von Buch's figures (figs. 4, 5, 6, of our plate), 

 has been already described ; it is the prevalent and most characteristic shape assumed by 

 the species. Next comes the — 



Rhynchonella (Atrypa) implexa, Sowerby. PI. XIV, figs. 7 — 10; Atryna implexa, 

 Sow., Trans. Geol. Soc, 2nd series, vol. v, PI. lvii, fig. 4, and of which Rhyn- 

 chonella {Terebratula) compta of Phillips, Pal. Foss. of Devon, at p. 89, pi. 35, fig. 

 161, is only a synonym, being a more elongated variety of the same form. 



Sowerby describes his Atrypa implexa as " Obovate transversely plaited. Front 



