334 
DEVONIAN PAUNA. 
1. Helminthochiton papilio, Whidhorne, sp. PI. XXXI, figs. 15, 15a, 16b, 16. 
1889. Chiton papilio, WJiidborne. Geol. Mag., dec. .3, vol. vi, p. 30. 
Description. — Plate elongate, narroAv, deep; posteriorly pointed; dorsally slightly 
convex ; laterally flat and very oblique, somewhat pinched in in front ; anteriorly 
deeply excavate, but with a broad, flat, slightly produced margin in the centre. 
Sides produced forwards into a kind of wing, so that the greatest length is about 
one and a half times that of the dorsal line. Margins of sides oblique, slightly 
convex, apparently bearing a small projection about half-way back, rapidly and 
evenly rounded in front ; inner margin of the wing nearly parallel with the outer 
margin. Surface obliterated but apparently bearing some raised oblique lines. 
Shell-structure thin except in the centre, where it is thickened by an indistinct 
rounded internal process crossing the centre of the valve, and running obliquely 
down the wings. No apophyses of insertion visible. 
Size. — Length of back 11 mm. ; total length 16 mm.; depth 10 mm.; width 
14 mm. 
Localities. — There is a specimen from Wolborough in the Museum of Practical 
Geology, and another from Lummaton in my Collection. 
Bemarks. — This species is only known by two detached median valves, which 
are not in a good state of preservation. It appears to have been a well-marked 
form, distinguished by its height and narrowness, and by the development of its 
wings. There seem to have been several raised lines near the extremity of the 
wings, almost parallel with the dorsal keel. The sides meet in an acute angle on 
the back forming a ridge which is slightly convex longitudinally. 
This description is taken from the specimen from Wolborough which is detached 
from matrix. My own specimen is very doubtful and indistinct, but though a 
little flatter it may, if a Chiton at all, have belonged to the same species. 
Affinities. — This species seems to come in general shape about midway between 
Chiton sagittalis, Sandberger,^ and Chiton corrugatus, Sandberger,^ differing, how- 
ever, widely from each. The former is a very much narrower shell : the latter is 
much broader, its posterior margins are concave, it is dorsally excavate, and it 
bears strong apophyses. Both species are strongly ornamented with concentric 
growth-strige. 
Helminthochiton Lehescontei, Barrois,^ is very similar in some respects, but difi'ers 
in having much smaller wings, in the margins being almost straight instead of 
' 1853, Saudberger, 'Verst. Khein. Kissau,' p. 239, pi. xxvi, figs. 23, 23 «, 23 
3 1853, ibid., p. 238, pi. xxvi, figs. 22, 22 a—d. 
3 1889, Barrois, ' Faun. Calc. d'Ebray,' p. 181, pi. xv, figs. 15 b. 
