THE 



GEOLOGICAL MAGAZINE, 



No. CVIIL— JUNE, 1873. 



I. — On Holaspis sericeus, and on the Kelationships of the 

 Fish-genera Fteraspis, Ctathaspis, and Scapbaspis. 



By E. Eay Lankester, M.A. 

 Fellow of Exeter College, Oxford. 

 (PLATE X.) 

 fpHE paper of Dr. A. Kunth, " Ueber Pteraspis," Zeitschr. der 

 JL Deutschen Geol. Gesellsch., 1872, Hft. 1, came into my hands 

 at a time when I had just been examining the specimen of which 

 a restored figure is given in the Plate accompanying this paper. I 

 took an early opportunity of replying to Dr. Kunth's adventurous 

 assertions in the Academy, and the remarks then made have been 

 reproduced in this Journal (April, 1873). I need, therefore, here, in 

 reference to that matter, only make one or two additional observa- 

 tions. Dr. Kunth based his statements on a single specimen in a 

 bad state of preservation. His figure shows how inadequate the 

 specimen is to support his views. Out of the many hundreds — I may 

 even say thousands — of specimens of Heterostraci which have passed 

 through my hands, I could easily pick several exhibiting all varieties 

 of juxtaposition of Pteraspis with Scaphaspis, and of specimens of 

 a single species of either genus with other specimens of the same 

 species. The packing of several shields one within another not 

 imfrequently occurs, as happens very generally in the embedding of 

 concave shells. The mere association of these shields, as in Gallicia 

 and in Herefordshire, is not a phenomenon on which any one 

 familiar with them — through examination of numbers of specimens 

 from various localities — would venture to base an}' argument as to 

 structural connexion. Dr. Kunth has been misled in this respect 

 by the isolation of his drift-block. The lateral piece between "head" 

 and "tail" shield, which Kunth accepts as a locomotive or mastica- 

 tory organ with so much facility, is simply an indefinite fragment ; as 

 are the supposed indications of a jointed body-structure or segments 

 lying between head and tail plate, which Kunth tells us are 

 altogether disarranged, and which he could not develope from the 

 matrix. If we were to proceed in Dr. Kunth's way in the interpre- 

 tation of some of our crowded specimens of Herefordshire Hetero- 

 straci, or with those slabs containing Scaphaspis shields and frag- 

 ments of every shape and size from the Cornish coast, it would be 

 easy to make out that the Heterostraci were turtles, crocodiles, 

 VOL. X.— NO. cvin. 16 



