340 Dr. Traqucdr — On Psephodus magmis,from E. Kilbride. 



one form apparently corresponding with the supposed " posterior " 

 tooth of M'Coy and Davis is provisionally referred to the lower jaw, 

 while another resembling the supposed " middle " tooth is in like 

 manner referred to the upper jaw.^ Moreover, on the 8th December, 

 1881, prior to the reading of Mr. Davis's paper, Mr. James Coutts exhi- 

 bited before the Geological Society of Grlasgow a remarkable specimen 

 of Fsepliodus magnus, discovered by Mr. A. Patton in the shale accom- 

 panying the cement-limestone of East Kilbride, and his remarks 

 upon it were published also in 1883.^ In this specimen we have 

 remains of the cartilage of the jaws, along with an aggregation of 

 teeth, which undoubtedly belonged to the same mouth. Concerning 

 the teeth here exhibited, Mr. Coutts remarks : — " The two largest 

 teeth evidently belong to Cochliodus magnus, or, as it is now given 

 in the ' Catalogue of Western Scottish Fossils,' Tomodus convexus, 

 Agassiz. Others of the teeth agree closely in form with Helodus 

 planus, now Fsepliodus magnus, Agassiz, thus confirming Captain 

 Jones's opinion that the teeth of Cochliodus magnus and Helodus 

 planus belong, in all probability, to the same fish. Some of the 

 teeth in this specimen agree very closely with Helodus mammillaris, 

 Agassiz, while others differ in form from any of the species indicated ; 

 indeed, it is very doubtful if there are any two teeth exactly alike, 

 but this is a feature common to the group of fishes to which the 

 specimen belongs." From the dates it will be seen that the 

 remarks of Mr. Davis and Mr. Coutts, on this form, were written 

 and published altogether independently of each other. 



Through the kindness of Messrs. Patton and Coutts, this very 

 interesting specimen has been entrusted to me for re-examination, 

 and in the present communication I pi'opose to give a more detailed 

 description of the facts and features which it displays. 



The specimen is contained on a nearly rectangular slab of shal« 

 9|^ inches in length by 4 in breadth. That which we may call the 

 anterior half of the surface (PI. YIII. Fig. l)*is occupied by remains 

 of cephalic cartilage, with teeth, behind which, on the posterior half, 

 we find some obscure remains of a vertebral column. The most 

 prominent object which strikes the eye on the anterior part of the 

 slab, and lying close to what may, for convenience, be called the 

 lower margin, is a piece of calcified cartilage, 3^ inches in length, 

 of an elongated form, gently curved, and broader behind than in 

 front, which one feels much tempted to regard as the ramus of a jaw. 

 Close to and slightly above the hinder extremity of this cartilage is 

 one of the large dental plates of Fsepliodus magnus (a), lying with 

 its deep or concave surface upwards ; but it may be lifted from the 

 matrix and freely examined on all sides. This dental plate (seen 

 isolated and from the convex surface in Fig. 3) is one of those trape- 

 zoidal teeth, considered as "middle" by M'Coy. All its margins are 

 crenulated, save the so-called inner margin, with which very dis- 

 tinct lines of growth run parallel. 



In front of this tooth, and extending to the anterior margin of the 

 slab, are seen many irregularly placed small Helodont teeth, above 

 * p. 64. 2 Xrans. Geol. Soc. Glasgow, vol. vii. pt. 1. pp. 164-166. 



