Bracuiopvopa. } LOWER PAL/EOZOIC MOLLUSCA. 203 
o 
This shell by its greater width in proportion to the length, greater gibbosity, and depth of front. sinus, 
distinct branching of outer pair of mesial ridges, &c. seems to be constantly distinguished from the H. crispata 
of Sowerby. As this is the only one of the several supposed varieties from different formations figured by 
Schlotheim, it is, I think, most correct to retain for it the present name, particularly when, as Mr Sowerby 
suggests, the supposed oolite examples may be the 7’. intermedia Sow. of the Min. Conchology, and this Silurian 
species may be the Anomia lacunosa of Linné. 
Position and Locality—Not uncommon in the Wenlock limestone of Wenlock, Shropshire. 
Hemitayris Lewisi (Davidson Sp.) 
Ref. and Syn. = Terebratula Lewisi David. Bull. de la Soc. Géol. de France, 2nd Series, Vol. V. 
tron 30: 
Sp. Ch.—Subrhomboidal or transversely oval; entering valve most gibbous, evenly tumid near the beaks, 
sides gradually curving towards the margin; mesial ridge prominent, obtusely rounded in the anterior half of 
the length, forming a very deep oblong sinus in the front margin; receiving valve convex near the beak, 
flattened at the sides, and with a deep wide depression in the anterior two-thirds of the middle; about nine 
strong angular ridges on each side, and two or four on the mesial ridge, and one or three in the corresponding 
ridges in the mesial sinus ; ridges crossed by sharp, scale-like transverse strize, most strongly marked near the 
margin; beak of entering valve small, much curved with a perforation beneath it; width of rather small 
specimen six and half lines, proportional length of receiving valve {,, length of entering valve jj, depth of both 
valves =; substance of shell fibrous. 
The greater width and more numerous lateral plaits separate it from the depressed varieties of the 
A. increbescens (Hall). Casts shew in the receiving valve two short, slightly diverging slits of dental lamellz, 
between which are three or four short diverging ridges, in the rostral portion; the entering valve shews a wide 
mesial slit of the thick septa, and impressions of two short cardinal teeth, just within the ends of the dental 
lamellee of the opposite valve. 
Position and Locality —Not wneommon in the Wenlock limestone of Dudley, Staffordshire ; in the black 
calcareous flags of Mathyrafal, S. of Meifod, Montgomeryshire. 
HemMitHyris Nasuta (J/°Coy). Pl. 1. L. fig. 5. 
Ref.—id. M°Coy, Ann. Nat. Hist. 2d Series, Vol. VIII. p. 393. 
Sp. Ch.—Longitudinally ovate, longer than wide, gibbous, entering valve much deeper than the receiving 
one; receiving valve with a small obtuse beak, incurved nearly to touch the beak of the entering valve, with 
a small triangular perforation beneath ; rostral portion tumid for about five lines from the beak, beyond which 
a wide, flattened, mesial depression is developed, gradually deepening towards the front, which in old specimens 
is very much produced into a flat tongue-shaped lobe, nearly as long as wide, gently sloping to the level of 
the most convex part of the entering valve; sides obtusely defined from the mesial furrow, gently convex ; 
lateral margins slightly sigmoid, and bent upwards at the front at a rounded angle of about 100°; entering 
valve with a slightly prominent beak: rostral portion and sides gently convex; after about five lines from the 
beak, the middle is prolonged nearly in a straight line to the produced front margin, forming a large obtusely 
rounded mesial ridge; surface radiated with simple, close, obtusely rounded ribs, about four of which, rather 
larger than the rest, are raised with the mesial furrow, the broad sides of which are smooth, each side with 
about twelve, slightly smaller ribs (seven in two lines at six lines from the beak near the side of the mesial 
furrow), leaving a rather broad smooth space at the rostral lateral margin on each side; (a fine longitudinal 
striation is seen in some parts). Length one inch two lines, proportional length of entering valve ;;;, greatest 
width about the middle of the length “, greatest depth of both valves (one-third from the beak) ;. 
In form this species much resembles the Terebratula promontorium of Kutorga from the lower Silurian 
limestones of Pulkowa, (see Verhandlungen der Russ. Kais. Min, Gesellschaft zu St. Petersburg, for 1845. 
t. 6. f. 3), but is distinguished by its ribbed surface. 
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