THE DOGFISH 



Acanthias vulgaris 



Two species of dogfish are common on the New England coast, 

 Acanthias vulgaris (Squalls acanthias) and Galeus canis.* Acanthias 

 has a stout spine in front of each dorsal fin and sharp and cutting teeth; 

 Mustelus lacks fin-spines and has flattened, pavement teeth. The follow- 

 ing directions are based upon Acanthias, but, except in regard to the exits 

 of the nerves through the wall of the cranium, will apply well to the 

 other form. 



Dealers supply Acanthias of three ages: 'pups,' about 8 to 9 inches 

 long; 'garters,' 18 to 20 inches long; and adults, from 2> to 3 feet total 

 length. For all purposes except the study of the brain and cranial nerves 

 and the fully developed sexual organs the ' garters ' are the most favor- 

 able. Each student will require two specimens, one for skeleton 

 and one for dissection, while an adult head for the brain, etc., is valuable. 

 Two students can readily compare specimens in order to see the other 

 sex. 



t The specimen for dissection should be injected. Dealers supply them 

 with the vessels filled with red and blue (or yellow, preferable), but it 

 is possible to inject formalin material. The arterial system is filled 

 by cutting off the tail behind the last dorsal fin and forcing the fluid 

 forward through the caudal artery. The venous system requires more 

 trouble. Inject, first, forward and back through the portal vein; second, 

 in both directions through one of the lateral abdominal veins; and third, 

 forward through the caudal vein which lies just ventral to the caudal 

 artery. 



* Some would refer the latter to the genus Mustelus, but the differences in 

 internal structure between Galeus and Mustelus are sufficient to warrant their 

 separation, even if there are no corresponding differences in the superficial 

 characters relied upon by the systematist. 



