152 



Magr. Fr. Schmidt — On Pteraspis Kneri. 



branches of Lindley and Hutton's original species of Halonia. Mr. 

 Dawes considered the alternate branches to be merely the impressions 

 of the tubercles which characterize the other species of Halonia. The 

 specimen I here figure shows that these lateral branches attained 

 to some length. In none of them is the natural termination shown. 

 The size and form of the scars at the broken ends indicate that the 

 branches were prolonged. 



EXPLANATION OF PLATE VII. 

 Fig. 1, Stem oi Bergeria giving ofi' a branch of Halonia regularis, Lindl. and Hutt. 



Drawn, two-thirds the natural size, from a specimen presented by Sir Ph. 



de M. Grey Egerton, Bart., to the British Museum. 

 Fig. 2. Internal cast of Halonia regularis, in the condition to which Goldenberg gave 



the name Cyclocladia. Two-thirds nat. size. From aspecimen in the Brit. Mus. 

 Fig. 3. Halonia regularis, with the leaf bases and scars of Lepidophloios. Natural 



size. From a specimen in the British Museum. 

 Fig. 4. One of the tubercles from Fig. 3, showing the persistent bases of the leaves 



surrounding the tubercle. 



II. — Note on Pteraspis Knurl 



By Magister Fr. Schmidt, 



Of the Imperial Academy of Sciences, St. Petersburg. 



IN the course of last summer I visited the banks of the Dniester, 

 in Podolia and Galizia, where I was fortunate in collecting, 

 near Zalesczyki, a number of shields belonging to Pteraspis 

 (ScapJiaspis) Kneri, Lank. 



As I observed that the shields of Pteraspis and ScapJiaspis always 

 occurred together, I was led to the conclusion that these shields 

 might, in all probability, belong to one and the same animal, 

 ScapJiaspis representing the ventral shield of Pteraspis'^ in the same 

 manner as in the genus Coccosteus, which possesses both a dorsal and 

 a ventral shield. 



Diagrams of the Shields of the several Genera of Heterosteacous CephalaspidjE 



(after Lank ester). 



--'O 



s s 



Fig. 1. Scaphaspis. Fig. 2. Cyathaspif. D 



-R = Eostrum,orEostral region. C=Cornua. i) = Central 



disc, or Discal region. (S = Posterior spine. = Orbits. 



Fig. 3. Pteraspis. 



[In order to render Prof. Schmidt's views more clear to the readers of the Geo- 

 ' See the " Placodermen des Devonischen Systems," by Pander, p. 4, 



