312 Davidson — On Syringothyris. 



In" 1863, as already stated, Professor Winchell describes (but does 

 not figure) his genus as " a shell with an elongated hinge -Hne. Ven- 

 tral valve with a mesial sinus, a very broad area, and a narrow 

 triangular fissure closed towards the apex by an external convex 

 pseudo-deltidium ; beneath which, and diverging from it, is another 

 transverse plate connecting the vertical dental lamellae arched above, 

 and beneath giving off a couple of median parallel lamellae which are 

 incurved so as to nearly join their inferior edges, thus forming a slit- 

 bearing tube, which projects beyond the limits of the plate from 

 which it originates into the interior of the shell. A low median 

 ridge extends from the beak to the anterior part of the valve ; dorsal 

 valve depressed, without area, with a distinct mesial fold." But in 

 order that the characters of the genus should be better understood, I 

 have figured in PL XIV. five drawings of Syringothyris typa, for which 

 I am indebted to Professor Winchell himself. Now, it has been 

 asked by Mr. Meek whether there may not occur at Millecent in 

 Ireland, and elsewhere, two closely similar but really very distinct 

 British types, confounded under the single specific denomination of 

 Sp. euspidata f — ^that is, one with a punctate structure, and another 

 without it ; and the examination of this question by Dr. Carpenter 

 has led him fully to adopt Mr. Meek's conclusion, as I shall presently 

 explain. 



Professor Winchell seems not to have been aware that the cha- 

 racters assigned by him to his genus had been already illustrated 

 and defined by Professor L. de Koninck in the Transactions of the 

 Koyal Society of Liege for 1859 ; and, as I made at the time some 

 better and enlarged drawings from the Belgian specimens, I will 

 reproduce them here along with M. de Koninck's original figure 

 (PI. XIV. Figs. 6-9). These characters were found to exist in a 

 Belgian example of the Carboniferous Spirifera ddstans. Pro- 

 fessor Winchell adds : " Some difficulty exists in deciding on 

 the homology of the transverse plate and fissured tube which 

 characterize this genus (Syringothyris). In the ventral valve of 

 Merista, especially of the type of Camarium Hall, an arching lamella 

 arises from the basal portion of each dental plate, and the two unite 

 in the mesial line of the valve, forming a structure which Professor 

 King, before the separation of this genus, had styled the shoe-lifter 

 process — arched in front and attached to the bottom of the valve 

 behind. In Spirifera granulifera Hall, a horizontal tranverse plate 

 stretches across the middle of the beak of the ventral valve, con- 

 necting the dental lamellas where nearest approximated by their in- 

 ward curvatures — a structure which probably represents the pseudo- 

 deltidium of certain Spirifera, but not of Gyrtia. Beneath this plate, 

 the ventral medium septum assumes the form of a tapering cone, 

 resting with its base fiUing the cavity, and having the anterior part 

 of the upper side marked by a longitudinal groove or slit, while the 

 posterior part sends up a small vertical plate to the transverse plate 

 just mentioned. In Syringothyris the tranverse plate equally con- 

 nects the dental lamellas where most approximated, and is somewhat 

 arched upwards as in Merista, but it does not join the bottom of the 



