288 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Mar. 25, 



of the plates is finely granular, and the exterior surface is charac- 

 terized by minute transverse striations ; whether the latter appear- 

 ance is attributable to a thin exterior integument or not, can only 

 be decided by microscopic examination ; indeed, many of the de- 

 tails I have alluded to are so minute., that the aid of a pocket 

 lens is not sufficient to enable me to offer them with any degree of 

 certainty, and the specimens are too precious to be mutilated for 

 more exact microscopical scrutiny. As Mv. Salter first directed my 

 attention to the structural peculiarities these specimens present, I 

 wish to name the species Auchenaspis Salteri. 



It remains for time and industry to determine whether the species 

 described above as Cephalaspis Murchisoni and Cepkalaspis ornatus 

 rightly belong to that genus, or whether they ought not to be re- 

 ferred to the genus Auchenaspis. The peculiar form of the hinder 

 margin of the cephalic buckler, so different from that of the typical 

 Cephalaspides, and yet corresponding with that of Auchenaspis, gives 

 some substance to the idea that it may have reference to the attach- 

 ment of nuchal plates ; and if so, these species must necessarily be 

 included in that genus. Much remains to be done with reference 

 to the structural anatomy and true affinities of this curious family — 

 subjects far beyond my grasp ; but which I trust ere long will be 

 grappled with and elucidated by Professor Huxley, who has already 

 bestowed some time upon them, and than whom no one is better 

 qualified for bringing the inquiry to a successful issue. 



Associated with the specimens described above, both in the railway- 

 cutting at Ludlow, and in the bed of the River Teme, Mr. Light- 

 body has discovered some other remains of fishes worthy of notice, 

 although too fragmentary to be accurately characterized. 



Of these, four specimens are portions of jaws corresponding generi- 

 cally with those described by Professor Agassiz under the name of 

 Plectrodus and resembling the Plectrodus tnirabilis rather than 

 P. pleiopristis * . Although at first sight the large laniary teeth 

 appear single, yet on closer examination the fractured surfaces are 

 distinguishable whence the lateral denticles distinctive of the genus 

 have been broken off. These teeth are grooved longitudinally, a 

 character not well shown in the specimens figured in the ' Silurian 

 System.' Fig. 4 is from the railroad, and figs. 2 & 3 from the fish- 

 bed on the river. 



The remaining specimens are Ichthyodorulites. One resembles 

 Onchus Murchisoni. The longitudinal ribs (fig. 6) certainly ap- 

 pear coarser than those in the specimens of this species already 

 figured ; but this may be accounted for by the fact that the specimen 

 only shows the dorsum of the ray, that portion in which the surface- 

 character is always more strongly marked than on the lateral and 

 posterior parts. This specimen is from the argillaceous beds in the 

 railway-cutting at Ludlow. 



A second species from the same locality appears to be undescribed 

 * Sil. Syst. p. 606, pi. 4. figs. 14-17, 21, 25, 26, & figs. 18, 19, 22-24. 



