89 
Genus Retzta (King). 
The typical species of this genus may be considered as in some respects related to the 
Rhynchonellide, but more closely to the Spiriferide, and in particular to the genus Spirigera. 
The shell is in yeneral small, and somewhat similar in form to Rhynchonella or to Terebratula, 
from both of which it is distinguished by the possession of calcareous spires. The shell-struc- 
ture, unlike that of Spirifera, is punctate ; but there is not an extended hinge-line, and there 
is either no true area or a small one. The beak of the ventral valve is perforated by a small 
foramen, and the surface is usually ornamented with radiating striz or ribs. The affinities of 
this genus are obscure, and it is uncertain what forms should properly be referred to it. Only 
one Brachiopod, viz.: Retzia Eugenia, (Billings), has been referred to this genus amongst the 
forms hitherto discovered in the Devonian Rocks of Ontario, and in the absence of any cer- 
tain knowledge as to its internal structure, it cannot be said that this reference is free from 
doubt. 
107. Rerzia (?) Eucenta (Billings). 
Retzia Eugenia (Billings), Canadian Journal, New Series, Vol. VI, p. 147, Fig. 58. 
“ Shell small, sub-globular, with from ten to twelve strong angnlar ribs on each valve. 
Ventral valve convex, most prominent on the upper half, a slight mesial depression the width 
of three or four of the ribs in the lower half ; beak elevated, incurved, but not in contact with 
the umbo of the dorsal valve, perforated at the point ; a flat solid deltidium or area beneath 
the aperture. Dorsal valve rather strongly and uniformly convex, most prominent along the 
middle, where slight indications of a mesial fold are evident ; umbo small, rounded ; beak 
buried beneath the lower edge of the deltidium or area of the ventral valve” (Billings). 
Average individuals appears to have a length of about four lines, with a width of about 
the same or slightly less; but larger and smaller examples are not unknown, 
I have seen only a few detached valves of this species, and can offer no opinion as to its 
real affinities. By Professor Hall it is considered, with some doubt, as being identical with 
his Trematospira gibbosa (Pal. New York, Vol. 1V., p. 272) ; but it is considered by Mr. Bil- 
ling to be distinct. 
Locality and Formation.—Rare in the Corniferous Limestone of Port Colborne. 
Genus LEtIoRHYNCHUS (Hall). 
“ The shells of this genus are ovate, circular, or transverse, with valves unequally convex, 
and marked by a median sinus and fold in the ventral and dorsal valves respectively. The 
surface is plicated by rounded bifurcating plications which are always more conspicuous on 
the mesial fold and sinus, whilst they often become obsolete on the lateral portions of the 
shell ; concentrically marked by strong lines of growth. Substance of the shell fibrous, usu- 
ally thin, Valves articulating by teeth and sockets; the apex of the ventral valve perforate 
at some period of its growth, the lower side being completed by deltidial plates. On the 
interior of the ventral valve, two short diverging dental lamell: extend into and are joined to 
the sides or bottom of the rostral cavity ; the muscular impression occupies a narrow triangular 
or ovate-triangular space, below the dental lamellz. The dorsal valve has a well defined 
septum, often reaching Lelow the middle of the valve, and divided above, leaving a triangular 
or spoon-shaped depression. The hinge-plates are narrow, strong processes, with sockets em- 
bracing the teeth of the opposite valve” (Hall, Pal. New York, Vol. IV., p. 355). 
I am notin the position to pronounce any opinion as to the validity of the genus Lezorhyn- 
chus, or as to the propriety of separating it from Rhynchonella, to which it is certainly most 
closely allied. In the meantime, I shall accept it for the reception of the following species 
from the Hamilton Group ; several allied species having been described by Professor Hall 
under this title from the Hamilton and Chemung Formations. 
108. LEIorRHYNCHUS MULTICOSTA (Hall). 
Leiorhynchus multicosta (Hall), Thirteenth Report on the State Cabinet, p. 85. 
Rhynchonella (?) Laura (Billings), Canadian Journal, New Series, Vol. V., Figs. 26-28. 
Letorhynchus multicosta (Hall), Pal. New York, Vol. IV., Plate LVI., Figs. 26-40. 
