348 MR. C. TATE REGAN ON SHARKS L-^W- ^8, 



in the sharks of this family is of some interest, and may be 

 exemplifiecl by compai-ison of two extreme types. 



Jthmodon typicus is a large pelagic shark, with numerous small 

 teeth, long gill-rakers, minute spiracles, and wide gill-openings ; 

 the pectoral fins are acutely pointed, and the axis of the caudal 

 fin is so strongly turned upwards and the lower lobe is so much 

 produced anteriorly as to give the appearance of a deeply forked 

 -symmetrical fin. The resemblances of this shark to the Basking 

 Hhark {Getorhinus onaximus), which belongs to the family 

 Lamnidse, are very striking. 



Eucrossorhinus dasypogon is a ground-shark with strong 

 dentition, large oblique spiracles, and small gill-openings ; the 

 head and anterior part of the body is strongly depressed and 

 fringed with dermal flaps ; the pectoral fins are broad and obtuse 

 and the axis of the caudal fin is not directed upwards nor is the 

 lower lobe enlarged. This form shows many points of similarity 

 to the Angel-fishes {/Squatma), which belong to another suborder. 



In some species (e. g. Chiloscyllium punctatumi, G. griseum, and 

 Stegostoma tigrinum) there is considerable variation in colour and 

 markings, partly due to changes wdiich take place during growth. 

 The young of these species have dark cross-bars, which may 

 become replaced by spots or may disappear, giving rise to a 

 uniform coloration. 



As a rule the pelagic forms (e. g. Ginglymostoma, Rhinodon) 

 have no conspicuous markings ; the littoral sh^axka {Parascyllium, 

 Brachcdurus, Chiloscyllium, Stegostoma) are spotted, barred, or 

 variously ornamented, the coloration being most brilliant in the 

 tropical species ; whilst the ground-sharks (Orectolobus, Eucros- 

 sorJiinics) have markings which probably resemble the rocks and 

 weeds among which they lurk. 



In the Orectolobidae, as in other sharks, the dorsal and anal 

 fins appear to be comparatively larger in the young than in the 

 adult. 



Synoi^sis of the Genera. 



I. Spiracles very small ; anal quite distinct from the caudal, 

 wholly or partly opposed to the second dorsal. 



A. Origin of second dorsal behind that of the anal ... 1. Farascyllium. 



B. Origin of second dorsal above or in advance of that 



of the anal. 



Teeth tricuspid or multicuspid 2. Gincjli/ mo stoma. 



Teeth unicuspid 3. Bhinodon. 



II. Spiracles well-developed; anal either continuous with 

 the caudal or terminating directly in front of it. 



A. Lower lip divided into two by a symphysial groove. 



1. Sides of head and snout without dermal flaps ; 



spiracle surrounded bj^ a circular raised rim... 4. JBracJieelurus. 



2. Sides of head and snout more or less strongly 



fringed with dermal flaps ; spiracles wide 



oblique slits. 



Last two gill-openings closer together than the rest 5. Orectolohns. 



Gill-openings equidistant 6. JSucrossorMiius. 



B. Lower lip not divided by a symphysial groove. 



Caudal fin of moderate length 7. Chiloscyllium. 



Caudal fin very elongate 8. Stegostoma. 



