168 FISHES. CHONDROPT. Lamna. 



we call the Thresher, from the motion of its long fox-like tail, with which it 

 strikes or thrashes its larger and less agile enemy, the grampus, whenever it 

 reaches the surface of the water to respire." 



Gen. XI. LAMNA. Porbeagle. — Branchial openings in 

 front of the pectorals. Snout conical. Nostrils at the 

 base below. 



15. L. cornubica. — Teeth produced, slender, with two pro- 

 cesses on each side at their base. 



Porbeagle, Borl. Corn. 265. tab. xxvi. f. 4. Penn. Brit. Zool. iii. 117., 



and Beaumaris Shark, ib. 118. tab. xvii., and 2d edition Squalus cor- 



nubicus, Goodenough, Linn. Trans, iii. 80. tab. iii. Donovan, Brit. 

 Fishes, tab. cviii. — S. Selanonus, Leach, Wern. Mem. ii. 64. tab. ii. 

 f. 2 — Not uncommon. 



Length from 5 to 9 feet. Colour bluish on the back, white on the belly. 

 Snout projecting. Pectorals semilunar, the first dorsal, nearly immediately 

 above. Ventrals small. Posterior, dorsal, and anal fins small, opposite. 

 Body contracted above and below at the setting on of the tail. Small tuber- 

 cles on the lateral line. A ridge extending from the tail on each side the 

 body towards the middle. Tail semilunar, the upper lobe rather largest. 

 This species is said to hunt its prey in companies. Its history as a British 

 fish has become much involved in error. Pennant, by adding the Beauma- 

 ris shark as a new species, Avhen, with the single exception of its apparently 

 shorter snout, its claims were insufficient, and by publishing an inaccurate 

 engraving from an accurate drawing by the Reverend Hugh Davis, introduced 

 the confusion. Donovan advanced a step towards a reformation, by having 

 examined the original drawing of Davis, and found it to correspond with the 

 Porbeagle. The editor of the edition (1812) of Pennant's British Zoology, 

 from a re-examination of the drawing of Mr Davis, asserts, that it " corres- 

 ponds exactly with the original plate ;" yet, by a management which seems 

 inexplicable, the engraving in the new edition is changed in many of its most 

 important features, so as to bear evident marks of differing from the former 

 plate, pronounced an accurate copy of the drawing. Dr Leach seems to have 

 described from a stuffed specimen of the Porbeagle his Squalus selanonius, sup- 

 posing it to be Dr Walker's new species S. selanonius, and which he regards as 

 similar to the Squalus maximus, The Porbeagle is ovoviviparous— It is oc- 

 casionally caught in the herring-nets. 



Squalus selanoneus This species was found by the late Dr Walker, in 



Lochfyne, in Argyleshire (whence the name from Lochfyne, Smus selanoneus 

 of Ptolemy), where it appears during the herring season. Stewart, in his 

 " Elements of Nat. Hist. i. 320.," inserts it in the section without the anal 

 fin, but with temporal orifices. In the description of this species in Dr Wal- 

 ker's MS. Adversaria for 176!), p. 155., now before me, there is no notice 

 taken either of the anal fin or temporal orifices, so that I am inclined to in- 

 fer the absence of both. Should this be the case, it will claim to rank as 

 a new genus, occupying a place between Charcharias and Lamna. I shall 

 here add the description as it appears in the original. " Caput, maxilla sub- 

 sequalis, superiore prominente, rostrata. Maxilla superior crassissima apice 

 truncata marginata, angulo superiori obtuso suberecto. Maxilla inferior an- 

 gusta. Dentes numerosi acuti. Oculi super cantham oris positi sunt. Cor- 

 pus, 8-pedale oblongum, teretiusculum, cute aspera. Spiracula 5, antico 

 breviore, erecta, lineari-lunata : margine postico curvato. Tria spiracula 

 postica super pinnam pcctoralem positi sunt, duo altera ante pi'nnam pectora- 



