. Bulletin of the British Museum (Natural History), Geology. (xiv) Squamation. The squamation of Macrosemius diplays two features of special interest. Perhaps most striking is the total absence of scales in a strip lying on either side of the dorsal fin, occupying from one-third to a quarter of the depth of the trunk. The squamation of this genus is further characterized by the presence of secondary scale rows which intervene between the trans- verse rows of the trunk in the region above the first longitudinal scale row dorsal to the lateral Une. This scale-pattern is described in ,
. Bulletin of the British Museum (Natural History), Geology. (xiv) Squamation. The squamation of Macrosemius diplays two features of special interest. Perhaps most striking is the total absence of scales in a strip lying on either side of the dorsal fin, occupying from one-third to a quarter of the depth of the trunk. The squamation of this genus is further characterized by the presence of secondary scale rows which intervene between the trans- verse rows of the trunk in the region above the first longitudinal scale row dorsal to the lateral Une. This scale-pattern is described in , below, in which the arrangement of the scales is more surely known. Below the lateral line the scales form a regular pattern of rectangles. These have been described in a young individual (P7177) by Schultze (1966 : 275, fig. 30). In the anterior region, ganoine is restricted to the denticles on the trailing edge of the scales. The bony layer is crossed by fine radial markings on the anterior half of each scale, and by concentric lines posteriorly. The ganoine- covered area of the scales increases in the caudal region, forming irregular patches. The abdominal scales of an older specimen are displayed in both lateral and medial view in AS. Here the ganoine layer is complete except for a narrow strip close to the anterior margin; the surface of the ganoine is smooth. Internally the scales forming the transverse rows are linked by small pegs-and- sockets. The shallow internal rib is inclined slightly in advance of the peg-and-socket. Schultze (1966 : fig. 16b) has drawn a lateral line scale in medial view. The sensory canal entered the anterior border of the scale close to the dorsal edge and continued through a thin-walled tube (collapsed in the specimen) which opens midway across the scale and continues as a narrow groove. A small pore, which presumably transmitted the sensory nerve, pierces the wall of the tube. Three large circumanal scales are preserved in 37094. The a
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