E. Etheridge, jun . — On some neio Carhoniferous Conchifera. 297 



found amongst existing forms. The shape of the shell somewhat 

 resembles that of certain living genera, as Creseis, Eang., and 

 Cuvieria, Eang. For further information respecting Conularia I 

 would refer those who take an interest in the subject to an article 

 by Dr. G. Sandberger in Leonhard and Bronn's Jahrbuch, 1847. 



IV. — On Some Undescribed Species of Lamellibranchiata feom 

 THE Carboniferous Series of Scotland. 



By R. Etheridge, Jun., F.G-.S. 



THE LamellihrancMata of the Scotch Carboniferous beds appear 

 to agree on the whole tolerably well with those of the series 

 as developed further south, notwithstanding we here and there meet 

 with well-marked varieties, and occasionally new species. These 

 are not so numerous as might have been expected when we take 

 into consideration the very different physical conditions which must 

 have existed during the deposition of the series in the two areas. 



In the present communication three forms will be noticed which 

 appear to be specifically distinct from any yet recorded from British 

 Carboniferous rocks. The first of these is an exceedingly well- 

 marked species of Conocardium, Bron. (PleurorTiynchus, Phil.), for 

 which I propose the name of Conocardium deciissatum, from the 

 characteristic ornamentation of the shell. It is a small species, 

 of a regular horse-hoof form, with an exceedingly strong ridge 

 separatiag the anterior and posterior sides, amounting almost to 

 a keel. In general form it resembles C. trigonale, Phil., and some 

 depressed varieties of C. Hibernicum, Sow., but may be at once 

 distinguished from both these by the shell-ornamentation. The 

 full description is as follows : 



1. — Conocardium decussatum, sp. nov. — Shell obliquely horse-hoof 

 shaped, very convex ; anterior end produced, somewhat cylindrical, 

 gaping, tapering towards the hinge-line ; posterior end truncatedj 

 slightly flattened, produced abruptly into an elongated siphonal tube 

 arising from the hinge-line, bounded by a very strong ridge or keel, 

 passing from the beaks to the antero-ventral extremity; beaks 

 nearly central, prominent, contiguous ; hinge-line as long as the 

 shell, terminating posteriorly in the siphonal tube ; surface cha- 

 racteristically ornamented ; the posterior end has from seven to 

 eight concentric ribs, which bifurcate about half-way between the 

 beaks and the shell-margin, and are crenulated along their whole 

 course; posterior end minutely and regularly decussated, the inter- 

 spaces assuming the form of elongated rhombs ; the crossings of 

 the radiating and horizontal striEe give rise to small nodes ; margin 

 crenulated. 



The truncated end of Conocardium is usually considered as anterior, 

 but I have followed the example of Woodward (Manual of Mollusca, 

 2nd ed., p. 455) and Baily (Journ. Eoy. Geol. Soc, Ireland, vol. iii. 

 pt. i. (n.s.) p. 24), by making the truncated end posterior. The 

 siphonal tube, although broken off, shows a decided tendency to 

 curve upwards. 



