302 
DEVONIAN FAUNA. 
sinus -band, and is differently marked. Mr. Roberts and I think that it is to be 
regarded as a new species of the Delphinuloides type. 
Affinities. — PL Larteti, (Ehlert,^ comes between this species and PI. delphinu- 
loides, being a more turbiniform shell without spiral strias. 
Pleurotomaria silurica, Eichwald,^ is rather similar in general shape. It 
differs in being more elevated and angulated, in having no spiral lines above the 
suture, and in having the transverse marks very coarse. 
PI. aspera, Sowerby,^ is a widely different shell with coarse reticulate markings 
and a convex sinus-band ; as also for the most part is Phillips' rendering* of that 
species. The four figures given by the latter author are, however, so dissimilar 
that it seems probable that he has included more than one species under this 
head. Three of these are totally distinct from the present form ; but the fourth, 
which he has separated from the rest, and described as " perhaps a cast of the 
above species," most probably represents an example of this shell. It is very 
similar in general shape, but Phillips' sketch seems to indicate that its ornamenta- 
tion was coarser. 
It appears very closely to resemble PI. cirriformis, Sowerby, sp., but differs in 
being less reticulate and more trochiform, in having the sinus-band smaller, less 
convex, and higher on the whorls, and in having a shallower suture. 
17. Pleurotomaeia Crokeri, n. sp. PI. XXVIII, fig. 14. 
Description. — Shell small, depressed, turbiniform, of few volutions. Spire 
forming a very low cone. Suture rather deep. Whorls elliptic in section, much 
wider than high, spreading out flatly from the suture with a gradually increasing 
curvature, very convex round the short back, and flattish on the base. Body- 
whorl very large. Sinus-band situate on the widest part of the whorls, elevated, 
convex, rather narrow, bounded by fine thread-like grooves, and marked by fine 
recurved striae. Surface smooth, or marked only by indistinct growth-lines. 
Size. — Height, 11 mm.; width, 17 mm. 
Locality. — Wolborough. There is a specimen in the British Museum, and 
another doubtful specimen in the Museum of Practical Geology. 
Bemarhs. — I have felt very doubtful whether these fossils were distinct, or 
whether they should be regarded as one of the numerous varieties of PI. delphinu- 
loides. They seem to differ from that species by having a narrower, convex, and 
1 1887, (Ehlert, ' Bull. Soc. d'Etude Sci. d'Angers,' p. 25, pi. ix, figs. 1, 1 a—e. 
2 1860, Bichwald, ' Lethsea Eossica,' p. 1171, pi. xliv, fig. 11. 
3 1840, Sowerby, ' Geol. Trans.,' ser. 2, vol. v, pt. 3, pi. liv, fig. 16. 
4 1841, Phillips, ' Pal. Foss.,' p. 96, pi. xxxvii, figs. 177 a—e, 177*. 
