VENOMS fN THE ANIMAL SERIES 



297 



Their poison-apparatus is placed in the dorsal fins, as in the case 

 of Scorpcena and Pterois. 



2.— Trachinidae. 



Genus Trachinus (Weevers).— Four species of AVeevers are 

 found in European seas: the Greater Weaver (Trachinus draco), 

 the Lesser Weaver (T. vipera), the Striped-headed AVeever [T. 

 radiatus), and the Mediterranean Spider AVeever (T. araneus) ; 

 other species are met with on the coast of Chile. 



AVeevers possess two sets of poison-apparatus, one of which is 

 situated on the operculum, the other at the hase of the spines of 

 the dorsal fin (fig. 107). 



Pig. 107. — Tracliinus vipera (Lesser Weerer). 



The spine surmounting the operculum exhibits a double can- 

 nelure connected with a conical cavity excavated in the thickness of 

 the base of the opercular bone. This spinels covered with a sheath, 

 beneath which he the secreting calls. The gland is an offshoot from 

 the skin, and appears as a simple follicle invaginated in the opercular 

 bone (fig. 108). 



The dorsal apparatus is composed of from five to seven spines, to 

 which the inter-radial membrane forms an adherent sheath which 

 extends almost to the end of the rays. Each spine exhibits a deep 

 double cannelure. The venom flows between the layer of calls cloth- 



