BRITISH FOSSILS. 



Decade X. Plates IV. and V. 



TRISTICHOPTERUS ALATUS. 



[Genus TRISTICHOPTERUS.* Egerton. (Sub-kingdom Vertebrata. Class 

 Pisces. Order Goniolepidoti. Family Ccelacanthi.) Body fusiform. Cranial bones 

 sculptured. Two dorsal fins ; one anal fin ; the rays of the second dorsal and the anal fin 

 springing from three strong interspinous bones in each. Caudal fin springing fi-om eight or 

 nine similar bones. Vertebral centres ossified and prolonged through the upper lobe 

 of the caudal fin.] 



Tristichopterus alatus, Sp. Unica. 



This is one of the many interesting additions made to the fossil 

 Fauna of Scotland by the zeal and intelligence of Mr. Peach. Two 

 specimens only have been obtained, one showing the general form 

 of the fish, with the exception of the extremities of the head and 

 tail, the other, with its counterpart, exhibiting in perfect preservation 

 the structural and other characters of the fins and tail. The 

 expanse of the latter and the opposition of the second dorsal 

 to the anal fin are characters which might lead one to refer this 

 form to the genera Di^lopterus or Gyroptychius, but a rigid ex- 

 amination of the specimens convinces me that it formed a member 

 of the Coelacanthoid family, although presenting some important 

 discrepancies from the other genera of that family. The points of 

 resemblance are seen in the number and position of the fins, the 

 curvilinear outline of the scales, and the prolongation of the central 

 portion of the tail. The difierences consist in the structural details 

 of the fins and the ossification of the vertebral centres ; but in 

 these respects the deviation from the Sauroidei-dipterini is quite 

 as great as from the Ccelacanthi, 



Description. — The more perfect of the two specimens measures 

 seven and a half inches in length ; if to this we add two and a 



* From rpets tres, ffTixv series, impov ala. 



