102 THE ASTEROLEPTS, 



as nearly as may be, a foot in length. If the Asterolepls was 

 formed in the proportions of the CoccosteuSy the buckler (tig. 

 29) must have belonged to an individual five feet in length ; 

 if in the proportions of the Pterichthys or Glyptolepis, to an 

 individual five and a half feet in length ; and if in those of 

 the Diplopterus or Osteolepis, to an individual of from six 

 and a half to seven feet in length. Now I find that the 

 hyoid plate can be inscribed — such is its form — in a semi- 

 circle, of which the nail-shaped ridge in the middle (if we 

 strike ofi" a minute portion of the sharp point, usually want- 

 ing in detached specimens) forms very nearly the radius, and 

 of which the diameter equals the breadth of the cranial buck- 

 ler, along a line drawn across at a distance from the nape 

 equal to two-thirds of the distance between the nape and the 

 eyes. Thus, the largest diameter of a hyoid plate which be- 

 longed to a cranial buckler a foot in length is, I find, equal 

 to seven one-quarter inches, while the length of its nail 

 somewhat exceeds three five-eighth inches. The nail of the 

 Stromness specimen measures five and a half inches. It 

 must have run along a hyoid plate eleven inches in trans- 

 verse breadth, and have been associated with a cranial buck- 

 ler eighteen one-eighth inches in length ; and the Asterolepls 

 to which it belonged must have measured from snout to tail, 

 if formed, as it probably was, in the proportions of its brother 

 Celacanth the Glyptolepis, eight feet three inches ; and if in 

 those of the Diplopterus^ from nine feet nine to ten feet six 

 inches. This early ganoid was at least as bulky as a large 

 porpoise. 



It was small, however, compared with specimens of the 

 Asterolepis found elsewhere. The hyoid plate figured in page 

 86 (fig. 40), — a Thurso specimen which I owe to the kind 

 ness of Mr Dick, — measures nearly fourteen inches, and the 

 cranial buckler of the same individual, fifteen one fourth 

 inches, in breadth. The latter, when entire, must have mea- 



