106 



BRITISH SILURIAN BRACHIOPODA. 



NucLEospiRA PisuM, Sow. (sp.). PI. X, figs. 16 — 20. 



SpimrER 1 PISUM, Sow. Silurian System, p. 630, p], xiii, fig. 9, 1839; and ' Siluria, 



2nd edit., pi. xxi, fig. 7, 1859. 



Spieifera — Phillips and Salter. Mem. Geol. Surv., vol. ii, p. 293, 1848. 



Spiuifee — Dav. Bull. Soc. Geol. France, 2nd ser„ vol. v, p. 325, 1848. 



— — Bronn. Index Pal., p. 1180, 1848. 



Atrypa — D'Orb. Prodrome, vol. i, p. 37, 1849. 



Hemythyeis?— M'Coy. Brit. Pal. Foss., p. 205, 1852. 



Orthis — Hall. Pal. New York, vol. ii, p. 250, pi. Hi, fig. 1, 1852. 



NucLEOSPiRA — Id. lb., vol. iii, p. 218, 1859. 



Spirigera ? — LindstrUm. Ofv. K. Vet. Akad. Fbrhandl., p. 3G1, 1860. 



Spec. Char. Shell small, suborbicular, very convex ; valves almost equally convex, and 

 gibbous near the beaks ; beaks very small, incurved, that of the ventral valve being a 

 little more elevated or projecting than that of the opposite valve; hinge-line straight, 

 much shorter than the width of the shell ; cardinal angles rounded ; sides and front 

 circular, or slightly narrowed and indented in front. Ventral valve a little deeper than 

 the dorsal valve, with a slight depression down its centre. Dorsal valve most convex 

 close to the umbone, with a faint line along its centre ; but after reaching to about the 

 centre of the valve, this line is gradually converted into a slight depression or sulcus. 

 False area small, triangular, with a depression in the middle. Surface of both valves 

 closely covered with long, slender, hair-like spines ; but when these are destroyed by fos- 

 silization, the shell appears smooth and minutely punctate. Interiorly, each of the spiral 

 coils is composed of six or seven convolutions, and are fixed to the hinge-plate of the 

 dorsal valve. Two specimens measured — 

 Length 4, width 5, depth 8 hues. 

 „ H, „ 5, „ 3 „ 



Ol/s. As will be seen from the list of references, this small shell has been placed in 

 no less than six difierent genera, namely, Spirifera, Atrypa, HemitUyris, Orthis, Spirigera, 

 and, lastly, in Nucleosjnra, where I trust it may find a permanent home. Dr. Lindstroni 

 informs me that Prof. Angelin named this ?,\)ec\e's, Terebratula pachyyaster'm his ' Musaeum 

 Palaeontologicum Suecicum,' 1838. At p. 205 of his ' Brit. Pal. Fossils,' while treating 

 of this shell. Prof. M'Coy states — " 1 have ascertained, by carefully breaking a specimen, 

 that there are no internal spiral appendages, and therefore the species does not belong to 

 Spirifer ; and I have observed a large triangular opening beneath the beak, so that 

 it does not belong to Atrypa, where ]\I. d'Orbigny has placed it." That Prof. M'Coy 

 should not have discoveied the spirals after breaking a specimen is not surprising, 

 and he might have broken twenty more without discovering a trace of their existence, 

 for they appear to have been very often destroyed in the process of fossilization. I have 



