200 BRITISH SILURIAN BRACHIOPODA. 
‘TRIPLESIA ? MONILIFERA, J/‘Coy (sp.). Pl. XXV, figs. 3—5. 
PRODUCTA MONILIFERA, M‘Coy. A Synopsis of the Silurian Fossils of ireland, p. 25, 
pl. iii, fig. 3, 1846. 
ORTHIS MONILIFERA, Etheridge. Catalogue of the Collection of Fossils in the Mus. of 
Practical Geology, p. 8, 1865. 
Spec. Char. Shell small, sometimes irregular, transversely oval, wider than long, 
broadest at about the middle of its length. Valves almost equally convex and deep. In 
the ventral valve a wide, deepish sinus commences at the front and disappears as it nears 
the beak, which is convex, pointed, and slightly incurved ; hinge-line straight and either 
slightly shorter or longer than the width of the shell; area triangular, of small elevation, 
with a narrow convex pseudo-deltidium along its middle. Dorsal valve divided into three 
lobes by a wide convex mesial fold. Surface of both valves ornamented by eight or nine 
almost parallel rows of continuous concentric ridges, each row being formed of continuous, 
bead-like, elevated tubercles. Between each row is a wide, slightly concave space. Interior 
unknown. 
Length 3, width 4, depth 2 lines. 
Obs. A single ventral valve of this curious little shell was, in 1846, figured and 
described by Prof. M‘Coy under the designation of Producta monilifera, and stated to 
be a miniature of P. pustulosus, Phillips. I admit that the aspect of this specimen, partly 
imbedded in the matrix, might naturally have led the distinguished Irlsh paleontologist 
to such an interpretation. Since that period, however, many perfect examples having 
turned up, it became easy to describe its external shape, and to show that it had nothing 
in common with Productus, although, being unacquainted with its internal arrangements, 
we cannot determine to what genus it should be referred. It is, however, probable or 
possible that my so termed Ziplesia Grayie' and the shell under description may belong 
to the same genus, for which Prof. Hall thinks a new name should be proposed. 
For the present, however, I prefer leaving the species with Zrzplesia, as I am averse 
to propose a new genus for a shell of whose internal character I am completely ignorant. 
T.? monilifera has also, like 7. Grayie, been found to vary much in shape on account 
of the twisted appearance the fold and sinus sometimes assume, and of these mal- 
formations a specimen is represented by fig. 5 of our plate. The concentric bead-like 
ridges are also strongly marked in some examples, while in others they are simply 
rows of unconnected elevated tubercles. I have not been able to clearly ascertain 
1 Prof. Hall writes, March, 1867—* Your little 7. Grayi@, on cutting down, seems to me to show a 
slender, closely coiled spire, somewhat as in Celospira or Alrypa, but there is only a single specimen 
showing it, and the condition of the others is not good.” 
