152 DEVONIAN FAUNA. 
1865. Leprmna INTERSTRIALIS, Davidson. Brit. Foss. Brach., vol. iii, pt. 6, p. 
85, pl. xviii, figs. 15—18. 
1867. — pPLANA, Trenkner. Paleont. Novit., pt. 1, p. 19, pl. iu, fig. 40. 
1867. _ AFFINIS, Trenkner. Ibid., p. 20, pl. iii, fig. 41. 
1867. SrRopHOMENA RADIATA, Trenkner. Ibid., p. 21, p. iii, fig. 44. 
1868. Lepr@Nna INTERSTRIALIS, Dames. Zeitsch. Deutsch. Geol. Gesell., vol. xx, 
p- 499, pl. xi, fig. 3. 
21874. SrropHoMENA VaRISTRIATA, Billings. Pal. Foss., vol. ii, pt. 1, p. 26, pl. 
iii, fig. 38. 
1884. — INTERSTRIALIS, Clarke. Neues Jahrb. f. Min., Beil.-Band 
iii, p. 400. 
1885. — af. CORRUGATELLA, Waldschmidt. Dev. Schichts. Wil- 
dungen, p. 907, pl. xxxix, fig. 1. 
1885. == INTERSTRIALIS, Maurer. Abhandl. Grossh. Hessisch. Geol. 
Landes, vol. i, pt. 2, p. 144, pl. 
v, figs. 17, 17 a. 
1887. — -- Tschernyschew. Mém. Com. Géol., vol. in, 
No. 3, p. 107, pl. xiv, fig. 19. 
1890. LEeprmna INTERSTRIALIS, Hhlert. Bull. Soc. Géol. Fr., ser. 8, vol. xvii, 
p- 776, pl. xix, fig. 10. 
1892. STrRoOPHEODONTA INTERSTRIALIS. Whiteaves. Contrib. Canad. Paleont. 
vol. i, pt. 4, p. 286, pl. xxxvii, fig. 6. 
Localities —From Lummaton there are about fifty specimens in my Collection, 
seventeen in the Woodwardian Museum, one in the Museum of Practical Geology, 
and twenty (?) in the Torquay Museum. From Barton there are six (including 
three which were figured by Phillips) in the British Museum. From Wolborough 
there is one specimen in Mr. Vicary’s Collection. 
Remarks.—This species shows a greater amount of variation than is indicated 
by Davidson. Some of the smallest specimens are either flat or geniculated, and 
have a few fine rays sunk in hollows between slightly convex interspaces, which 
are covered by minute radiations and strong transverse puckerings. As the 
shell increases in size the ventral valve becomes evenly convex, the major rays 
become stronger and more numerous, and at last form high indefinite ridges, while 
the interspaces become concave, and the puckerings usually, but not always, 
vanish, so that the fine secondary radiation alone remains. In this stage it is 
distinguished from small specimens of L. nobilis chiefly by its fewer and coarser 
ribs, and by the absence of puckerings, at least on the marginal parts. In other 
examples the minor rays seem obliterated, the interspaces between the major ribs 
being either concave or convex, and themselves ornamented by a few coarse ribs. 
Thus it is seen that the variations are not constant with the size, but at the same 
time the gradations are so perfect that there is no doubt that the shells all belong 
to one species. 
It still seems an open question whether it is distinct from L. nobilis. The 
