No. 1.] WHITEAVES — NEW SPECIES OF PTERICHTHYS. 25 



deur d'une bonne tete d'epingle, et ils sont places en series line- 

 aires plus ou moins regulieres, formant des lignes ondulees sur la 

 surface de I'^caille. Pour la plupart, ces creux sont isoles lesuns 

 des autres, quelquefois aussi plusieurs se confondent en formant 

 Tin sillon plus ou moins long. Las carenes iutermediaires sont 

 tranchantes et minces, maisellcsse maintiennent au meme niveau; 

 Ton ne pourrait donner une meilleure image de cette sculpture 

 des plaques, qu'en enfon§ant des epingles, la tete la premiere, sur 

 le gyps encore frais, car il en resulterait le meme dessin. En exa- 

 minant ces pla^jues a la loupe, on voit au fond de cliaque cellule 

 osseuse un petit trou central, qui mene dans un canal meduUaire 

 de I'int^rieur de I'ecaille. Evidemment ces trous etaient destines 

 a donner passage aux fins vaisseaux sauguinsqui montaient a tra- 

 vers I'ecaille pour se ramifier dans I'epiderme qui couvrait la pla- 

 que." All the markings so carefully described in the above 

 passage, even to the minute perforations through the plate in the 

 centre of each pit, can be made out with perfect ease in most of 

 the specimens collected by Messrs. Ells and Weston. 



The Canadian Pterichthys is so closely allied to the Bothrio- 

 lepis ornata that it is by no means certain whether the two are 

 specifically distinct or not. Apart from its peculiar sculpture, 

 the specific characters of of B. ornata are very imperfectly ascer- 

 tained, the species having been founded exclusively on a fewlarge 

 isolated plates of a placoderm, from the Devonian rocks of Russia 

 and Scotland. Until more perfect examples of j8. ornata shall 

 have been described and figured, it will be impossible to institute 

 an accurate comparison between it and the nearly related Cana- 

 dian form. There are, however, good reasons for supposing that 

 the European species attained a much larger si^e than the 

 Canadian, for Agassiz says that the plates of jS. ornata are from 

 three to six inches in length, and judging b}^ this, the approx- 

 mate length of its helmet and buckler together may be roughly 

 estimated at from six to twelve inches at least. The largest 

 isolated plate of the Pterichthys from the Baie des Chaleurs yet 

 obtained (one of the ventro-laterals) is only two inches and a 

 half long, while the smallest of two perfect specimens of the 

 united helmet and buckler from the same locality is a little over 

 two inches in length, and the largest (the fine specimen collected 

 by Mr. Ells) is just six inches. 



Under the circumstances, the writer thinks it most prudent to 

 give to the Canadian Pterichthys a local and provisional name, 



