8 BRITISH PERMIAN BRACHIOPODA. 



short longitudinal riband-shaped lamellae, which are other oblique and diverging ones (6) attached to those 

 soon united by a transversal lamella, which is more already described, and fixed to the bottom of the 

 or less bent upwards in the middle (L). This simply shell (PI. I, fig. 19). From these proceed the longi- 

 attached loop is confined to the posterior portion of tudinal branches of a short simple loop (A), similar 

 the shell, and does not exceed much more than one in character to that of Terebratula proper. A minute 

 third of the length of the valve. There are no mesial ridge extends from under the cardinal pro- 

 sloping hinge-plates attached to the bottom of the cess ; these plates, with their central interspace and 

 valve, as in T. elongata and kindred forms, nor mesial ridge, form a lozenge-shaped elevation (PI. I, 

 lozenge-shaped elevation. The quadruple impres- fig. 18, also woodcut). On either side of this pro- 

 sionsof the adductor muscle (A) being impressed on cess, and extending further down, are seen the 

 the bottom of the shell, exactly under the short sim- quadruple impressions left by the adductor (A), as 

 pie loop, the diverging grooves (m) passing uninter- dispayed in the accompanying cut. 

 ruptedly through them. 



From the above it will be perceived that the differences between Terebratula proper 

 and Epithyris, as typified by Professor King in 1850, are chiefly confined to the presence 

 of prominent dental or rostral plates in the one, and almost total absence in the other, as 

 well as differences in certain details connected with the hinge-plate. On the other hand, 

 the exterior characters are similar, the deltidium being more or less concealed in certain 

 individuals than in others, from the greater or lesser approximation of the foramen to the 

 umbonal beak. 1 This is also the case in many species of true Terebratula. In the interior 

 the loop is the same, short, and simply attached, the longitudinal branches being united 

 by a transversal band, more or less bent upwards in the middle. 2 The muscular impres- 

 sions appear also similar, as well as the intimate shell-structure. 



It will therefore be for palaeontologists to determine whether the differences observable 

 in the rostral cavity of the beak and hinge-plate of these few Palaeozoic Terebratula should 

 be considered of sufficient value to counterbalance the great resemblance they present with 

 Terebratula proper in their more important dispositions and characters. 



Terebratula elongata, Schloth., sp. Plate I, figs. 5 — 22 ; and Plate II, fig. 2. 



A difference in opinion has been expressed by some British and foreign palaeontolo- 

 gists relative to the respective specific claims of Ter. elongata and T sufflata of Schlotheim. 

 These shells are so extremely variable in their shape, that Professor King could not help 



1 I am rather surprised that Professor M'Coy should have doubted the presence of a deltidium in 

 T. hastata, T. elongata, and other similar shells, for it may be seen in many individuals, and more 

 especially in young shells. 



2 Professor King states that " Waldheimia is most intimately related to Epithyris ;" that "in Wald- 

 heimia the loop is elliptical, deeply recurved, and projecting about two thirds of the length of the shell ; 

 but that in Epithyris it is semi-elliptical, moderately recurved, and projecting about one third of the 

 length of the shell." I do not perceive any important differences in its loop and that of Terebratula ; 

 moreover, Professor King admits that his illustration, pi. vi, fig. 45, was not quite correct. 



