o/ Platjsomus and a new Amphicentrum. 255 



tlon of the sliale at Newsliam, without which valuable privi- 

 lege much of our knowledge of the palaeontology of the Low 

 Main could not have been attained. 



Amphicentrum striatum, n. sp. 



A new species of this rare and interesting genus has been 

 found at Newsham ; seven or eight specimens have been ob- 

 tained. It differs by well-marked characters from the A. granu- 

 latum, Huxley, the only other known member of the genus, and 

 it is much smaller. The contour of the new species is rhombic, 

 the trunk being a little wider than long, measured from angle 

 to angle ; the dorsal and ventral angles are not much produced. 

 The head is small and conical, with the muzzle forming the 

 anterior angle ; the upper and lower margins are continuous 

 with the dorsal and ventral lines of the trunk. The cranial 

 bones are too much disturbed to admit of particular descrip- 

 tion ; they are, however, covered with a lustrous enamel, and 

 are ornamented with strong stri^ and tubercles, which irregu- 

 larly run into each other. The fins are almost entirely want- 

 ing in our specimens ; only one of them shows a little of the 

 dorsal, which appears to be very delicate ; and another a por- 

 tion of the caudal. 



The scales are well preserved in three or four specimens. 

 They are oblong, perhaps somewhat rhomboidal, and are much 

 longer than wide ; the peg is long ; they become smaller to- 

 wards the dorsal and ventral margins of the trunk, where they 

 are strongly tuberculated : the large central scales, of which 

 there are three series in depth, have their extremities also a 

 little tuberculated ; but their middle and greater portions are 

 covered with strong, somewhat irregular, raised, longitudinal 

 strise ; so that the trunk of the fish has tuberculated dorsal 

 and ventral belts, with the central portion striated. 



The V-like arrangement of the dental tubercles, so far as 

 we have been able to examine it, is the same as in A. granu- 

 latum ; and the mandibular dental plates, which are frequently 

 found detached, do not seem to dift'er in any important respect 

 from those of that species, size being the chief distinguishing 

 feature. The length of the body, including the head, is two 

 inches, and its depth from the dorsal to the ventral angle an 

 inch and three quarters. 



This is a very beautiful species, and is at once distinguished 

 from its congener by its small size and, particularly, by the 

 striaj on the middle portion of the body, Avhich ornamentation 

 contrasts well with the strong marginal tubercles, the whole 

 being coated with brilliant enamel. 



