RHYNCHONELLID A. 201 
whether there existed or not a small foramen at the extremity of the beak of the ventral 
valve. 
Position and Locality. T.? monilifera is known from the Caradoc or Bala Limestone 
only. In England it was found by Prof. Harkness at Keisley, Dufton, in Westmoreland. 
In Ireland it was obtained by Prof. M‘Coy and others at the Chair of Kildare, County 
Kildare. It is not known to me from any other locality, British or foreign. 
Before describing the numerous species composing the genus Orthis, it may be 
desirable to make known four which we cannot at present refer with certainty to any 
genus as yet established. ‘The family, also, to which they belong, as well as that of 
Hichwaldia Capewelli, Triplesia Grayiea, T. ? Maccoyana, and T.? monilifera, described 
in the preceding pages, will require to be hereafter determined. It is to be hoped that 
the discovery of specimens exhibiting internal characters will before long enable palzon- 
tologists to assign to these doubtful forms their true place in the classification. 
Cyrtia? nasuta, Lindstrom (sp.). Pl. XXV, figs. 1, 2. 
STROPHOMENA NASUTA, Lindstrém. Ofv. K. Akad. Forhandl. Stockholm, 1860, p. 371, 
pl. xii, fig. 15. 
Spec. Char. Shell small, somewhat obscurely pentagonal or transversely oval, not 
always very regular in shape, slightly broader than long, greatest width anteriorly, taper- 
ing at the beak ; hinge-line straight, shorter than the width of the shell. Ventral valve 
convex, beak nearly straight, and truncated at its extremity by a minute circular foramen ; 
area triangular, about one fourth as high as long; deltidium very narrow and convex. 
Sinus deep, angular, and becoming obsolete as it nears the beak ; three or four short, not 
very regular, or equally wide, or straight ribs occur on each of the lateral portions of the 
valve, but do not extend to much more than half the length of the valve from the margin. 
Dorsal valve convex, rather less deep than the opposite one, and divided along the middle, 
more or less regularly, by a prominent angular fold, which, commencing at a short distance 
from the umbone, extends to the front; three or four short ribs are also present on the 
lateral portions of this valve, and the surface of both valves is crossed by numerous more 
or less strongly marked concentric or scabrose ridges of growth. Interior unknown. 
Length 3, width 33, depth 2 lines. 
Obs. Of this curious little Spirifer-shaped shell, I have seen four British and two or 
three Swedish examples. ‘They were all more or less irregular in the shape and position 
of their fold, sinus, and ribs, which is chiefly to be accounted for by the fold and 
sinus being twisted more to one side than to the other. They all, however, possess the 
same essential characters of area, deltidium, and apicial foramen, as well as the same general 
26 
