from Achanarras Quari-y^ Caithness. 485 



there being five on the right and only four on the left. Thej 

 are proportionally narrower than in Megalichthys^ but not so 

 narrow as in Osteoleins. 



12. Clidrolepis TrailU^ Ag. — Two specimens of this from 

 Achanarras are in the Museum of Science and Art, and one in 

 the collection of the Geological Survey, and I also observed 

 some fragments of the same species in the dtSbris of the quarry. 

 I have no hesitation in referring these specimens, the first of 

 the genus ever observed in Caithness, to the same species as 

 that which is so common in the Orkney as well as in the 

 Moray-Firth beds. 



13. Palceospondylus Gunniiy g. et sp. n. (fig. 4, mao-nified). 

 — This is hitherto the only novelty which has turned up in 

 the quarry, and it is of excessive in- 

 terest, though unfortunately it must Fig, 4. 



take its place among the fossil fisiies 

 incertce sedis. It might indeed be asked, 

 Where is the evidence that it is even a 

 fish ? though there is no doubt of its 

 being a Vertebrate. 



This little organism varies from 1 

 to 1^ inch in length, of which measure- 

 ment the head occupies about a fifth. 

 Little can be made out of the struc- 

 ture of the head, which looks like a 

 flat crushed mass of bony bars; it Palcsosponch,lus Gunnii, 

 is a little longer than broad, with a Iraq., twice nat. size, 

 slight lateral hour-glass constriction, 



rounded in front and truncate behind ; from the front two 

 small, short, pointed processes project, one on each side, 

 like a pair of little feelers, while behind a little shield-like 

 body passes back over the first three or four vertebrse. Nothing 

 at all comparable to jaws, upper or lower, can be seen. The 

 vertebral axis, whicli passing back from the head becomes 

 attenuated to a fine point posteriorly, is composed of distinctly 

 ossified and separate vertebral centra, which, however, appear 

 to me to be hollow or ring-like, as in Chondrencheli/s &c. In 

 the anterior two thirds of the vertebral column the neural 

 arches are distinctly seen in the type specimen, but they are 

 not furnished with prominent spines ; but in the latter third 

 very slender obliquely-directed spines make their appearance 

 both neurally and hsemally. 



Not tlie smallest trace^ of limbs has been seen in any 

 specimen. 



