~ RHYNCHONELLIDA. 179 
Hyporayris DEFLEXA et BREVIROSTRIS, Phillips and Salter. Memoirs of the Geol. 
Survey, vol. ii, p. 280, 1848. 
ATRYPA INTERPLICATA, J. Hall. Paleont. New York, vol. ii, p. 275, pl. lvi, figs. 2 
a—g, 1852. 
RHYNCHONELLA DEFLEXA, Salter. Siluria, p. 544, pl. xxii, fig. 10, 1859. 
_— —  Lindstrim. Gottlands Brach., p. 366, 1860. 
Spec. Char. Transversely oval or subovate, wider than long. Dorsal valve ventri- 
cose, especially at the middle and umbone, which last is higher, much incurved, 
and projecting beyond the small closely incurved beak of the ventral valve. Mesial fold 
broad, but scarcely rising above the general convexity of the valve. Surface ornamented 
with from twelve to thirty angular ribs, of which from three to nine occupy the fold. 
Ventral valve most convex at the beak, which is small. Mesial sinus wide and deep, 
commencing at a short distance from the extremity of the beak, and gradually widening 
till it reaches the front. Surface of valves ornamented with from eleven to twenty-nine 
angular ribs, of which from two to eight occupy the sinus. Some of the ribs are also due 
to interpolation, and the whole surface of both valves is closely crossed by numerous 
fine, concentric, slightly projecting lines of growth. Proportions variable ; two specimens 
measured— 
Length 9, width 8, depth 6 lines. 
oD ha AG 1558: 
Obs. In 1848 I had made out that 7. drevirostris and T. spherica of the ‘ Silurian 
System,’ were synonyms of 7. deflexa ; and Mr. Salter subsequently added 7. interplicata 
of the same author and work to the synonyms of the species under description. ‘They are 
all simple modifications in shape and age of a single well-characterised species ; indeed, 
its short closely incurved beaks and ventricose dorsal valve might at first sight lead one to 
imagine that the ventral valve was the dorsal one, but such is certainly not the case. It 
varies also in the number and strength of its ribs, as may be seen by the figures in our 
plate. We are not acquainted with the interior. 
Position and Locality. 'Yhe vertical range of this species is not very great, for we 
know it only from the Woolhope Limestone and the Wenlock Limestone and Shale. It is 
common in two last-named rocks at Dudley, Benthall Edge, Wenlock Edge; Lincoln 
Mill, near Walsall, &c. Phillips and Salter mention its presence under Worcester 
Beacon and Croft in the Malvern district, east of Hill End in the Abberley district, 
Checkley Common, Dormington Wood, and Woolhope, Woolhope district. Between Rock 
and Dursley Cross, May Hill district; Pwll-Calch, Llandeilo district, and at Ballard’s 
Quarry in the Woolhope beds. 
_ In Ireland it has been found by the Geological Survey at Cahirconree, west side, 
County Kerry, in rocks of the Wenlock age. It has not yet been found in Scotland. 
Abroad it occurs in the Island of Gothland; in Bohemia; and at Lockport, 
