Foord and Crick — On Prolecanites compressus. 15 



specimen at the point where the suture-line was seen to be present, 

 alter very careful examination we have been able to satisfy ourselves 

 that the first lateral lobe is not divided, as M'Coy's figure indicates, 

 but that it terminates in a single point ; and further, that the 

 peripheral (or external) lobe is not V-shaped, as M'Coy represents, 

 but that it is shaped somewhat-like the lateral lobes, being slightly 

 contracted above, expanded below and terminating in a rather acute 

 point. We notice that at one part of the specimen the peripheral 

 lobe appears to be V-shaped, but the posterior portion of the lobe is 

 not sharp, and the whorl has here been gi'ound away to a depth of 

 more than one-half of a millimetre, a considerable amount, since 

 the height of the whorl when complete was only nine millimetres. 



In all the specimens of "Ammonites HensloioV that we have been 

 able to examine, the peripheral lobe is V-shaped, but as we have 

 not been able to observe the periphery of a young shell, i.e. of a 

 shell of about the same diameter as M'Coy's Goniatites discus, we 

 cannot say if at this age the peripheral lobe is V-shaped or if it has 

 the form of the lateral lobes, as in M'Coy's species. 



Although the latter is evidently closely allied to Sowerby's species, 

 M'Coy's G. discus appears to have been not only a less rapidly 

 increasing, but also a smaller shell, for in the specimen above 

 referred to, which is about 42 mm. in diameter, about one-third of 

 the last whorl is occupied by the body-chamber. 



We do not think it possible that Sowerby's ElJipsolites compressus 

 can be a badly-preserved specimen of what he later on described as 

 Nautilus complanatus,^ from the Carboniferous Limestone of Scarlet 

 in the Isle of Man, for, in describing the latter shell, Sowerby states 

 that the periphery is rounded, and it must be observed that his type 

 has, according to his figure, a large portion of the body-chamber 

 preserved. Further, in the latter species the greatest thickness of 

 the whorls is at the margin of the umbilicus, whereas in EUipsolites 

 compressus it is at about the middle of the lateral area. 



We arrive, therefore, at the conclusion that Mr. Wright's specimen 

 is specifically identical with the two examples figured by Sowerby 

 as Ellipsolites compressus, and that all three specimens are examples 

 of the species which Sowerby described later as Ammonites Henslowi. 



(iv.) Observations on the Name of the species. 



Having established the identity of Sowerby's Ellipsolites compressus 

 with his Ammonites Henslowi, it remains for us to offer some remarks 

 upon the name of this shell. 



(a). First as to the genus : — 



In the first place we will consider the name Ellipsolites compressus. 



The genus Elliysolites was founded by Denys de Montfort' in 

 1808, his type being E. funatus, a cretaceous Ammonite from Mount 

 St. Catherine, near Rouen. To de Montfort's genus Sowerby referred 

 three species from the Carboniferous Limestone, Blackrock, near 



' Mill. Con., vol. iii. 1820, p. 109, pi. 261. The type-specimen is in the 

 Woodwardian Museum, Cambridge. 



^ Gonchyliologie systematique, 1808, vol. i. p. 86. 



