﻿RHYNCHONELLA. 



63 



find Sowerby's original specimen, and feel somewhat uncertain as to the value of the 

 species as well as of its identification. 1 



Rhynchonella pugnus, Martin. PL XII, figs. 12 — 14, and PL XIII, figs. 8, 9, 10. 



CoNCHYLiOLiTiius anomites pugnus, Martin. Petrificata Derbensia, tab. xxii, figs. 



4, 5, 1805. 



Atrypa pugnus, Sow. Geol. Trans., 2nd ser., vol. v, pi. lvi, figs. 15 — 18. 

 Terebratula pugnus, Phi/lips. Palaeozoic Fossils of Devon, &c, p. 87, pi. xxxv, fig. 

 156, 1841. 



anisodonta, Phillips. Ibid., p. 86, pi. xxxiv, fig. 154, 1841. 

 Rhynchonella pugnus, Dav. Mon. British Carb. Brach., p. 97, pi. xxii, figs. 1 — 15. 



This well-known Carboniferous species has been fully described in the second volume 

 of the present work. It occurs, but not abundantly, in the Upper Devonian limestone 

 of Petherwin, and Landlake, in Cornwall, and in the Middle Devonian limestone of 

 Woolborough quarry, near Newton Abbot ; at Barton, near Torquay, and Plymouth, in 

 Devonshire. 



Bhgn. pugnus varies exceedingly in shape and character, both in the Carboniferous and 

 Devonian formations, and among its varieties may, I think, be placed Rhynchonella 

 {Terebratula) anisodonta of Phillips, which the author last named describes as " trans- 

 versely elliptical, depressed ; the front straight, the beak rather prominent. Front large 

 and angularly raised to a straight mesial edge, deeply indented by six intervening narrow 

 rounded ridges : sides rather reflected towards the deep valve, and very deeply and 

 broadly notched by short acute bold ridges." 



As is the case with the greater number of specimens of Bh. pugnus, the ribs become 

 apparent only near the margin, and do not usually extend over what corresponds to the 

 visceral portion of the shell ; their number is also very variable in different specimens, 

 those on the fold numbering three, four, five, and six in different examples. 



Prof. Phillips states that, on comparing his specimens of B. anisodonta with some 

 of the numerous and apparently distinct varieties of Bh. pleurodon alluded to in his work 

 ' On the Geology of Yorkshire,' he finds it difficult to doubt their close affinity. I am, 

 however, more disposed to consider their affinity to be much closer to Bh. pugnus than 

 to Bh. pleurodon, considering that in this last-named species the ribs radiate from the 

 beak and umbone to the margin, while in Bh. anisodonta, as in Bh. pugnus, they become 

 apparent only in the proximity of the margin, the remainder of the shell being smooth. 

 The var. anisodonta occurs along with true Bh. pugnus in the Middle Devonian limestone 



1 Atrypa subdentata, Sow. Trans. Geol. Soc, 2nd series, vol. v, pi. liv, fig. 7. 



" Orbicular, slightly convex, rather longer than wide, with a pointed three-plaited raised front : 

 beak minute. Loc. Petherwin." 



