RORQUALS 151 



tribes, who use the decaying mud of marshes the 

 effect in this case being tetanus. 



The Rorquals are among those whales that have 

 preserved a trace of the primitive hairy covering. 

 There are a few hairs present in the adults of these 

 whales, and in an embryo of B. sibbaldii van Beneden 

 figures eleven hairs on each side of the upper jaw and 

 four on each side of the lower. 



A highly characteristic feature of the Rorquals is 

 the series of longitudinal folds in the throat region. 

 They share these with the genera Rhachianectes and 

 Megaptera alone among whalebone whales ; but the 

 Ziphioids have a few folds in the same region, which 

 are possibly comparable. 



The number of these folds in species of Balanop- 

 tera varies somewhat. B. rostrata has been stated 

 to possess 54-60 ; in B. sibbaldii Turner counted 60. 

 A larger number, according to Murie, characterises 

 B. muscuhis, for in a specimen of that whale he 

 estimated the total number at about 100. These 

 folds, although spoken of as throat folds, really reach 

 further back than the throat region indeed, to a 

 point considerably behind the attachment of the 

 pectoral fin. Kukenthal, as well as long before him 

 -Eschricht, have pointed out that these folds are 

 not found in the youngest embryos a fact which 

 renders their comparison with the apparently corre- 

 sponding folds of the Ziphioid whales unlikely. In 

 B. muscnlus they were first visible in an embryo of 

 more than 60 cm. long. The meaning from a physio- 

 logical point of view of these folds is to be sought 



