Bracutopopa.] DEVONIAN MOLLUSCA. 389 
irregular, interrupted, transverse wrinkles, rather stronger at the sides; entering valve very concave, similarly 
marked to the receiving valve, the projections being inward. Width of large specimen one inch, length 
of receiving valve =, of entering valve 4, depth of receiving valve “, of entering valve 4. 
It is remarkable that neither Mr Sowerby nor Prof. Phillips, (Pal. Foss.), noticed the identity of our British 
fossil with that described by Sir R. Murchison from Boulogne. The elongation of the tubercles in Mr 
Sowerby’s figure, t. 54. f. 3, is, I find, only produced by mechanical compression in the rock, the part of the 
specimen not crushed having them round. The young specimens rarely shew any of the obsolete concentric 
wrinkles, and in them also the spine bases are more nearly round; they are fewer, more distant, and less 
regular than in the 2. spinulosa (Sow.), and the peculiar form of the tubercles, their number, and tuberculation 
of the entering valve, as well as less gibbosity, separate it from the P. aculeata. The spines are usually more 
than their diameter apart, and are slightly closer on the sides than on the middle of the shell. 
The fewer and more distant rounded tubercles distinguish this from the P. granulosa (Phill. = P. papillosa 
de Kon.) 
Position and Locality.—Very common in the slate and subordinate limestone of S. Petherwin; and in 
the same slate at Lanlake, Launceston. 
Subgenus. LEPTAGONIA. See page 247. 
LeptanA (Leptagonia) ANALOGA (Phill. Sp.) 
Ref. and Syn.= Producta analoga Phill. Geol. York. Vol. II. t. 7. f. 10. Pal. Foss. f. 98 a> Leptena distorta 
(Sow.) Min. Con. t. 615, f. 3. ¢> Lepteena nodulosa (Phill. Pal. Foss. f. 94), (and rugosa same plate, f. 95, 
not of Dal.) 
The shell in the middle and upper Paleozoic rocks can scarcely be considered a distinct species from the 
L. depressa of the Lower Palzeozoic strata (which see), and of which probably it is only a variety, not separable 
when the extremes are compared, but generally recognisable as a distinct variety, much in the same way as 
the Devonian variety, aspera, of the Silurian Spirigerina reticularis, is usually distinguishable from the older 
varieties. The general characters of the species are exactly those of the Z. depressa, and the description 
given in the Lower Paleozoic section of that species will suit the present in nearly all respects. The differences 
which strike an observer are, that the transverse wrinkles in the Lower Paleozoic LZ. depressa are usually from 
twelve to fifteen in number, but in this variety are from fifteen to twenty, most usually about eighteen, and the 
longitudinal striz are on the average considerably coarser in the Z. analoga than in the L. depressa: in the 
middle of the front, at the angle between the visceral portion and deflected front of the Lower Palzeozoic form, 
from nine to twenty of these strize may be counted in the space of two lines, twelve being the most common 
number; but in the ZL. analoga, in the same space, and at the same part, there are from four to ten, most 
usually eight. Thus, though one might procure specimens from the mountain-limestone or the Silurian rocks, 
to agree in either of these characters, yet from the lower strata I have never seen specimens approaching 
the coarseness of striation of the mountain-limestone or Upper Devonian ones, nor have I ever seen Silurian 
specimens with such numerous concentric wrinkles as are commonly seen in carboniferous ones. As to the 
varieties named Leptena distorta by Sowerby, and Lepteena nodulosa by Phillips, I have in the mountain-lime- 
stone traced all the intermediate varieties to the more regular types, and no doubt exists in my mind of their 
specific identity. 
Position and Locality —Very coarsely striated var. in Upper Devonian slate, on road a quarter of a 
mile S. of Marwood. 
9th Family. PRODUCTID. 
Shell free, without cardinal area or perforation for a muscle of attachment; no cardinal teeth to receiving 
valve, nor free internal testaceous appendages to entering valve. Surface set with tubular spines (arms and 
other soft parts supposed to resemble those of Lingula). 
