10G OLD RED SANDSTONE FISHES. 



Both/riolepis, from which it is, however, distinguished in shape by the wide 

 re-entering angle in front for the reception of the back part of the head. 



The anterior median dorsal plate (a. m. d.) is peculiarly short and broad, and on 

 the external aspect (Fig. 7, PL XXII) shows a blunt longitudinal elevation in the 

 anterior half of its length. As usual, it is overlapped behind by the posterior 

 median dorsal ; laterally it first overlaps and is then overlapped by the anterior 

 dorso-lateral, behind which it is overlapped by the posterior dorso-lateral as in 

 Pterichthys and Bothriolepis. These relationships of the anterior median dorsal 

 to the surrounding plates may be easily understood by comparing Fig. 7 on PL 

 XXII with the outline of the dorsal plates seen from within given in the appended 

 text-figure. 



The anterior dorso-laterals (a. d. I.) are remarkable for the length of their outer 

 margins and the oblique direction of their anterior borders, whereby the angularly 

 excavated contour of the front of the carapace is brought about. The posterior 



Fig. 56. 



Dorsal plates of the carapace of Microbrachius Bicki, seen from the internal aspect; the outlines of 

 the head and of one of the arms are likewise shown. 



dorso-laterals are broad and, as already mentioned, overlap the posterior part of the 

 outer margin of the anterior median dorsal. The posterior median, dorsal (p. m. d.) 

 largely overlaps the hinder margin of the plate in front, and as shown in Fig. 56 

 projects backwards in a prominent sharply pointed process. 



The ventral surface of the carapace (PL XXII, Fig. 8, magnified) is peculiarly 

 narrow in proportion to the breadth of the dorsal aspect, and the free extremities 

 of the posterior ventrolaterals (p. v. I.) are almost always seen projecting behind the 

 posterior median dorsal in specimens viewed from the back. The median ventral 

 plate (m. v.), or at least its exposed area, is very small. 



The exposed surfaces of the body plates are ornamented by a very fine 

 granulated or tuberculated sculpture, which in the anterior median dorsal tends to 

 coalesce in concentric lines (Fig. 7). 



The pectoral limb is short as in Pterichthys. The form and number of its 

 individual elements cannot be made out, but a prominent serration of its outer 

 margin is distinctly enough seen in most of the specimens. 



