8 SPHYNID^R - RENICEPS. 25 



the middle line of. the back, ending in a pit at the root of the tail ; pec- 

 toral fins -rather large; veutrals .small. Color gray; caudal fin with a 

 conspicuous narrow blackish edge. Newfoundland to South America ; 

 common southward. Size rather small. 



(Squalus (Carcharian) terrce-uorce Ricliarrlson, F. B. A. Hi, '289: (htrSutrlax icrrm.-uwce 

 Gunther, viii, .560.) 



FAMILY VIII. SPHYRNIDJE. 



(The Hammer -headed Shark*.) 



General characters of the Galeorhlnidas, but the head singularly formed, 

 kidney-shaped or "hammer "-shaped from the extension of its sides, the 

 nostrils being anterior and the eyes on the sides of the '"hammer"; 

 mouth crescent-shaped, under the "hammer"; the teeth of both jaws simi- 

 lar, oblique, each with a notch on the outside near the base ; no spira- 

 cles; last gill-opening over the pectorals; first dorsal and pectorals 

 large, the dorsal nearer pectorals than veutrals ; second dorsal and anal 

 small; a pit at the root of the caudal; caudal fin with a single notch 

 towaid its tip, its lower lobe developed. Genera 3; species 5 ; inhabiting 

 most seas. Large sharks, known at once by the singular form of the 

 head, ((^irchariida'^ part: group Zygasnma Giiuther, 380-383.) 



* Nostrils near the eyes. 



a. Nostrils simple, with Ihe frontal grooves rudimentary or obsolete ; head reni- 

 form, its anterior and lateral margins confluent, forming a semicircle. 



RENICEPS, 22. 



aa. Nostrils "with grooves extending in front toward the middle of the head ; 

 head truly hammer-shaped ................... .... .......... SPHYRNA, 23. 



22. RENICEP Gill, 1861. 

 Bonnet-headed Sharks. 



(Gill, Ann. Lye. Nat. Hist. N Y. 1861, viii, p. 412: type Squahis Hbnro L.) 



Head reniforin, the anterior and lateral margins confluent, forming 

 a regular semicircle, the posterior margins of the sides of the hammer 

 very short; nostrils close to the eyes, with the grooves indistinct. 

 (Latin, rena, kidney ; ceps, head.) 

 31. R. tlBjlBl'O (L.) Gill. Shovel-head Shark ; Bonnet Head. 



Body rather slender, not much compressed ; head depressed, semicir- 

 cular in front, reniforin, the posterior free margins short, the lateral mar- 

 gins continuous with the anterior; pectorals large; first dorsal high, 

 midway between pectorals and vein rals ; second dorsal much smaller, 

 produced behind, higher and shorter than anal; ventral fins moderate; 

 caudal moderate; mouth small, crescentic; teeth small, very oblique, 

 with a deep notch on the outer margin. Color uniform ashy, paler 



