CLASS ELASMOBRANCHII 



431 



SUBCLASS II. HOLOCEPHALI. - -The members of this subclass 

 differ from the SELACHII in a number of minor structural char- 

 acters. There is a single family, the CHIM^RID^;, containing 



77V 



FIG. 367. Chimczra monstrosa, male, m, mouth; n.p, frontal clasper: 

 op, operculum. (From the Cambridge Natural History.) 



three genera. The species shown in Figure 367 is the sea-cat 

 of the North Atlantic. 



3. THE ECONOMIC IMPORTANCE OF ELASMOBRANCHS 



Many destructive species belong to the elasmobranchs. The 

 smooth dogfish shark, Mitstclus canis, is an important enemy of 

 the lobster. It is estimated that the minimum number of lob- 

 sters destroyed by these dogfish sharks in Buzzards Bay during 

 one year is about 640,000. The sand-shark, Carcharias Uttoralis, 

 devours large numbers of valuable fishes, including menhaden, 

 flounders, and scup. The horned dogfish shark, S qualm acan- 

 thias (Fig. 358), is the most serious destructive agency with which 

 fishermen have to contend. It devours valuable food fishes, 

 drives away or destroys schools of squid used by the fishermen 

 for bait, and robs and injures nets and other fishing gear. Experts 

 estimate the damage from dogfish sharks to marketable fish and 

 fishing gear owned in Massachusetts at not less than $400,000 

 per year. They suggest that dogfish sharks be converted into 

 oil and fertilizer so as to make it profitable for fishermen to 

 capture them and thus bring about a decrease in their numbers. 



