206 BRITISH PALALOZOIC FOSSILS. [ Bracnropopa. 
Differs from the Permian Terebratula superstes (Vern.) in the greater width of the shell and wider 
and shallower wave in the front margin. 
I have not ever seen a moderately good specimen of this species, and am consequently uncertain of the 
genus. 
Position and Locality.—Sandstone of Alt Goch, Llanfyllin, Montgomeryshire, (one very imperfect cast). 
HEMITHYRIS SPH#ROIDALIS (J/°Coy). Pl. 1. L. fig. 4. 
Ref—id. M°Coy, Ann. Nat. Hist. 2nd Series, Vol. VIII. p. 398. 
Sp. Ch.—Suborbicular, gibbous, nearly equivalve, margins very obtuse from the inflection of the edges ; 
lateral margins nearly level, front margin abruptly raised into a quadrate sinus, about twice as wide as long ; 
receiving valve with a very small, pointed, slightly incurved beak, with a minute triangular perforation beneath 
it, evenly gibbous, except close to the sinus in the front margin, where there is a very slightly-marked 
depression ; entering valve evenly gibbous, with a very slightly-marked broad square ridge, extending a short 
way from the margin of the sinus; both valves radiated with from twenty to twenty-four very obtuse, rounded 
ribs, becoming gradually obsolete near the beaks, leaving the rostral portion nearly smooth; four of the 
ribs rather larger than the rest, slightly elevated with the mesial sinus; a short mesial septum in the 
entering valve; substance of the shell densely fibrous. Length five lines, proportional width ,°;, proportional 
depth of both valves *. 
The depressed spheroidal form, and very obtusely rounded ribs becoming obsolete towards the beak, 
distinguish this species from the H. nucula; and the elevation of the mesial sinus being towards the entering 
instead of the receiving valve, as well as more depressed form, distinguish it from the Terebratula spherica, 
and Terebratus deflexa of the Wenlock rocks, to which it is otherwise very similar. This seems to be the 
upper Silurian species referred to by Mr Davidson as identical with the Devonian Atrypa sphwrica of Sowerby, 
to which it is very strongly allied, but is more depressed, has only four mesial ribs, and the beak is not 
adpressed. The obtuseness of the plaits and smooth rostral portion separate it from the Zvrebratula pusilla 
(Sow.) of the Lower Silurian rocks. The very obtuse margin and smaller number of mesial plaits, and obtuse 
inflated form, separate it from the Terebratula famula of Barrande (see Haidinger Naturwissenschaftliche 
Abhandlungen, Band 1. t. 17. f. 6.) 
Position and Locality —Not uncommon in the Wenlock limestone of Dudley, Staffordshire ; Wenlock 
limestone of Ledbury, Herefordshire ; and the limestone of the Hollies, Church Stretton, Shropshire. 
Explanation of Figures—P1 1. L. fig. 4, Profile, natural size, from the limestone of the Hollies; 
4a, front view; 40, entering valve. 
HeEMITHYRIS STRICKLANDI (Sow. Sp.) 
Ref. and Syn. = Terebratula Stricklandi Sow. Sil. Syst. t. 13. f. 19. 
Sp. Ch.—Ovato-subtrigonal, beak of the receiving valve very small, flattened, and closely pressed over the 
beak of the opposite one, which is obscurely bilobed by a longitudinal mesial depression ; apical angle 130°; 
receiving valve much smaller than the other, flattened or gently convex at the sides, and in the third of the 
length near the beak, sinking abruptly into a deep, wide, mesial hollow towards the margin, which is lifted 
thereby into a deep, oblong, slightly rounded sinus, the corresponding flattened ridge to which in the opposite 
valve extends only half-way to the beak; ridges close, narrow, angular, simple, all extending nearly to the beak, 
but leaving a narrow, elliptical, smooth space at each side, usually eight raised with the sinus, the outer pair 
often becoming obsolete at the margin, eight or ten similar ridges on each side; plicated part of the lateral 
margin nearly straight ; the sides of some specimens shew a few coarse longitudinal strize towards the margin. 
Length one inch one line; proportional width =, length of entering valve >, depth of both valves =; tissue of 
shell fibrous. 
It is very seldom that any perforation can be seen under the singularly small, depressed, beak of the 
receiving valve. 
Position and Locality—Not uncommon in the Wenlock limestone of Sedgley, near Dudley, Staffordshire. 
