272 THE FISHES OF MALABAR. 



Group PEISHSIDJi. 



Genus PRISTIS, Latham. 

 Pkistibatis, Blainville. 



Snout prolonged, flattened, and laterally armed with numerous flattened, trenchant teeth, which are 

 directed almost directly outwards, commencing from in front of the nostril and continued almost to its 

 termination. .Nostrils some distance anterior to the mouth, each with a narrow, long, triangular valve at 

 its upper margin, and a hem-like one at its lower. Mouth straight and transverse, having a membraneous 

 transverse valve with a straight lower margin behind the teeth in the upper jaw. Spiracles large, separated 

 by a broad bridge from the eyes. Upper eyelid without a projection. Teeth flattened like paving stones. 

 Anterior dorsal partly above the ventral, the two dorsals of equal size. Caudal short, with or without a 

 lower lobe. 



Peistis semisagittatus. 

 Squalus semisagittatus, Shaw, Zool. v. pt. II. p. 361; Cantor, Catal. p. 407 ; Dumiril, 



Ich. gen. i. p. 477. 

 Yahla, Russell, pi. 13. 



Snout extended anteriorly into a flattened bone, armed with laterally compressed teeth directed 

 outwards, and varying from twenty-four to thirty-five on a side, whilst there are six or seven more 

 on one side (generally the right) than on the other. In the immature the teeth are only situated 

 in the last three-fourths of the snout, whilst in the foetus they are not apparent. The first six pairs 

 of the anterior teeth in the adult are opposite, their front edge rather convex, their posterior 

 barbed at their inferior third. 



Mouth transverse with a transversal membraneous valve (fringed in the young) behind the 

 teeth in the upper jaw, and with a deep notch near the symphysis. No cartilages exist at the 

 angle of the mouth. The upper eyelid has no projection. The pupil is transverse, with one semi- 

 circular flap above and another below ; these flaps are easily raised, depressed, or expanded, 

 apparently at the pleasure of the fish, or perhaps according to the stimulus of light received, which 

 they can partially or entirely exclude : lens very soft. Spiracles large, posterior to the eyes, from 

 which they are separated by a broad ridge. Anterior branchial aperture placed just below the 

 origin of the pectoral. Nostrils situated about their transverse length from the mouth, each has 

 a long triangular narrow valve in its upper, and a hem-like one at its lower margin : they are 

 three-fourths of their length apart posteriorly, and one and a half times anteriorly, whilst exter- 

 nally they are close to the margin of the snout. 



Teeth — Flattened like paving stones. 



Fins — The first dorsal commences opposite the posterior end of the ventral : the second dorsal 

 midway between the posterior extremity of the first dorsal and the base of the caudal. The two 

 dorsals are of equal size, their anterior extremities one-third longer than their posterior ones, their 

 upper margins concave, and their posterior rather produced. Posterior margin of the caudal deeply 

 excavated so as to form two lobes. The external margin of the pectoral concave, its posterior 

 margin rather more than one-third the length of its anterior. 



There is a sharp ridge or keel laterally along the tail between the sides and the abdominal 

 surfaces. The male appendages are joined by then- anterior two-thirds to the inner margins of 

 the ventrals. 



