A NEW GENUS OF GANOID FISH. 4G1 



I. Description of a Male Calamoichthys calabaricus : — 



Male. — A specimen measuring nearly 12| inches in total length. (See 

 Plate XXXI. figs. 1, 2, 3, 5, 6.) 



Head. — The head is small, being less than one-twelfth of the total length of the 

 body ; depressed above, and rounded in front ; it bulges out laterally, a little 

 behind the orbits, and contracts again towards the back part, and the narrower 

 neck of the fish. The front of the snout, sides of the head including the eye, 

 and back to the opercular plate, are covered with a soft, smooth skin. On each 

 side of the snout, in front, is a small projecting tubular cirrus, forming the 

 external nasal openings; these cirri are about \ of an inch apart, and each 

 measures ^j of an inch in length ; at the distance of \ of an inch behind them, 

 and \ of an inch from the point of snout the orbits are situated, at the junction of 

 the superior and lateral parts of the head. The orbital openings are small, 

 measuring rather more than ^ of an inch across ; and from the back part of the 

 orbit to the upper and posterior angle of the opercular plate, it measures f of an 

 inch in length. 



A series of bony plates very similar in their arrangement to those of the genus 

 Polypterus, commences a little behind the nostrils, and passing above the orbits, 

 covers the whole upper portions of the head. These plates are arranged in 

 pairs, one on each side of a nearly straight mesial line or suture ; they are the 

 exposed portions of the cranial bones, and are sculptured on their surface, like the 

 scales of the body, and are also ganoid in their character. Beginning in front, a 

 little behind the snout, there is, first, a pair of small rhomboidal-shaped plates, 

 the nasal bones ; these are rounded in outline in front, lie immediately on each side 

 of the mesial line, and pass backward to the front of the orbits, where they 

 are separated by a transverse wavy suture from the pair of plates immediately 

 above and beyond them. The next plates are the frontal bones, the largest of 

 the cranial plates; rather narrow in front, they become gradually broader at 

 the back part of the orbit, and contract again in breadth as they proceed 

 backwards, to meet, by a transverse suture in front of the spiracular openings, 

 the next pair of plates, the parietal bones ; which lie immediately behind them in 

 the mesial line. The parietal bones or plates are somewhat quadrate in 

 shape, but longer than broad ; they are longer than the nasal plates, but are 

 about a third shorter than the frontal bones, and they terminate posteriorly in a 

 nearly straight transverse suture, which separates them from the small supra 

 occipital plates or bones, two in number on each side of the mesial line, which 

 cover the upper and back part of the head, at the nape of the neck. The internal 

 supra occipital plate, that next the mesial line, is the longest and largest, being 

 about a third longer than the external plate ; it is somewhat rhomboidal in shape, 

 and terminates in a rather rounded posterior extremity. The external supra 

 vol. xxiv. PART II. 6 I 



