TEREBRATULA. 9 



observing, that Schlotheim considered some of their varieties as species, 1 and that he him- 

 self has no decided objection to that view, but feels utterly unable to separate one from 

 another, as they merge so imperceptibly into each other. Professor King admits but two 

 out of Schlotheim's several species, viz., T. elongata and T. sufflata ; this view has also 

 been reciprocated by Professor M'Coy. 2 On the other hand, Dr. Geinitz, 3 Baron 

 Schauroth, 4 Mr. Howse, 5 and a few others, consider that there exists no valid grounds for 

 even separating specifically T. sufflata from T. elongata, and either entirely amalgamate 

 the two under the single denomination of the last-named shell, or consider sufflata in the 

 light of a named variety. 



Having had the opportunity of examining a very numerous series of both, I experienced 

 the same difficulties in the attempt to separate T. elongata and sufflata. No doubt, if 

 certain typical, or what might be considered typical shapes of both are selected, we might 

 perceive certain peculiarities in each, and be tempted, perchance, to create more than one 

 species ; but these variations seem to exist only in certain individuals, while every interme- 

 diate form would be found in the same bed, and even quarry, to connect these different 

 extremes. Such being the case, I have preferred to follow in the path of those authors 

 who, while admitting but one species, have retained sufflata for the variety. 



Terebratula elongata, var. gentjina. Plate I, figs. 5 — 7, 12 — 14, and 18 — 22. 



(King's Mon., pi. vi, figs. 30 — 45.) 



Tebebeatulites elongatus et complanatus, Schlotheim. Akad. Munch., vol. vi, p. 27, 



pi. vii, figs. 7—14, 1816. 



When full grown and well shaped, it is more or less elongated, widest near the 

 middle, with almost equally deep, convex valves. The beak is more or less attenuated and 

 incurved ; the foramen rather small and circular, lying close to the umbone of the dorsal 

 valve, so that the deltidium is but rarely exposed. The larger or ventral valve is mode- 

 rately convex, presenting in profile a regularly arched curve from the extremity of the beak 

 to the front, with a wide and gradually depressed or shallow sinus, commencing towards 

 the middle of the valve, and extending to the front in almost all well-shaped examples ; 

 it produces in the frontal margin a convex and elevated curve, varying in degree accord- 

 ing to age and individuals. 



1 ' Monograph of English Permian Fossils,' p. 148, 1850. 



- 'British Palseozoic Fossils,' pp. 409, 412, 1855. 



3 ' Die Versteinerungen,' p. 11, pi. iv, fig. 27, April, 1848. 



* ' Em neuer Beitrag zur Palseontologie des deutschen Zechsteingebirges,' p. 213, 1856. 



5 'Annals and Mag. of Nat. Hist.,' vol. xix, 2d series, p. 52, 1857. 



