108 OLD RED SANDSTONE FISHES. 



situated on the median occipital, while each lateral limb runs obliquely forwards 

 and outwards close to the main groove on the lateral plates. Anterior median 

 dorsal plate overlapping the anterior dorso-lateral, but overlapped by the posterior 

 dorso-lateral plate. Pectoral appendages at least as long as the carapace ; in the 

 proximal segment on the outer aspect the articular plates are in contact for some 

 distance above the external marginal, while on the dorsal aspect the anconeal 

 is reduced to a very small rounded plate, thereby permitting the external and 

 internal marginals to come into contact with each other between it and the 

 articular ; distal portion of the appendage narrow and tapering. Tail not usually 

 preserved ; apparently not provided with ossified scales. 



History. — This genus was founded by Eichwald, in 1840, 1 upon certain plates 

 or fragments of plates occurring in the Upper Devonian of Russia, which differed 

 from those of Asterolepis in having the surface pitted instead of tuberculated. 

 From his very brief original description it is evident that he had before him frag- 

 ments of a creature allied to Pterichthys ; but unfortunately he ascribed teeth to it, 

 and imagined that its scutes were arranged in longitudinal rows like those of the 

 sturgeons. 



In the " Tableau Generale " prefixed to the first volume of the ' Poissons 

 Fossiles ' Agassiz applied the name Glyptosteus reticulatus, but without description, 

 to similar plates both from Russia and from Scotland. But in the ' Poissons 

 Fossiles du vieux gres rouge ' he adopted Eichwald's name Bothriolepis, though 

 giving the genus a place in his family of " Celacanthes," and including in it an 

 undoubted Rhizodont, with fluted laniary teeth, which he described and figured as 

 B. favosus. 2 It is also to be noted that in the same work he described as 

 Pterichthys major, Pam/phr actus hydrophilus and Andersoni, Homotltorax Flemingii, 

 Placothorax 'paradoxus, Odontacanthus crenatus and heterodon, remains which have 

 all turned out to be referable to Bothriolepis of Eichwald. By Pander, indeed, not 

 only these genera, but also Bothriolepis itself, were considered to be simply 

 synonymous with Asterolepis.' 6 



The near affinity, at all events, of Bothriolepis to Asterolepis was acknowledged 

 in 1860 by Eichwald, 4 who, though still keeping the two genera separate, placed 

 them close together in the family of " Placodermes." His statement is very clear 

 that " Le corps du Bothriolepis est compose de plaques, et peut-etre aussi cl'organes 

 a ramer semblables a ceux de Y Asterolepis," and the figure given represents an 



1 " Die Tliier- und Pflanzen-reste des alten rotlieu Sandsteins und Bergkalks im Novgorodschen 

 Grouvernement," ' Bull. Sci. St.-Petersbourg,' April, 1840. 



2 Eeferred by Smith Woodward to Hall's genus Sauripterus, ' Cat. Foss. Fishes Brit. Mus.,' pt. ii, 

 1891, p. 365. 



3 ' Placodermen,' p. 44. 



4 ' Lethsea Eossica,' vol. i, p. 1513, pi. lvi, fig. 3. 



