I02 



SMITHSONIAN MISCELIvANEOUS COLLECTIONS 



VOL. 52 



lateral branchial apertures and the broad isthmus between them. 

 The skull is differentiated into three regions — a broad, subquadran- 

 gular, postocular portion, an abruptly contracted, narrow, interocu- 

 lar region, and a wider preocular or rostral region. The armature 

 of the head is weak, only one pair of conspicuous spines being de- 

 veloped, a single one about the hinder angle of the preopercle ; there 

 are, however, rudiments of two or three 



imore below. There are a number of 

 genera, especially in northern Asia, several 

 of which are peculiar to the great lake 

 Baikal and others to Japan. ^ 

 The name-giving genus, Cottus, embraces 

 nearly fifty species, most of which are very 

 much alike and difficult to discriminate. 

 They are most numerous in the northern 

 portions of America and Asia, and less so 

 in Europe ; but in the latter continent is to 

 be found the longest and best-known species, 

 Cottus gobio. 

 Millers-thumb is the most generally used name for the species of 

 the genus in England. Yarrell explains how it came into use : "The 

 thumb, by a peculiar movement, spreads the sample over the fingers 

 and, employed with tact, becomes the gauge of the value of the meal 

 produced. Hence the saying, 'Worth a miller's thumb.' " The 

 thumb of the miller of the olden time became thus spread out be- 



FiG. 28.— Skull of fresh 

 water Millers-thumb. 



Fic. 29. — Skull of Millers- 

 thumb. After Girard. 





V.V 



';f/ 



Fig. 30.~Cottiis gobio. After Smitt (W. v. Wright). 



neath the nail, and a likeness was fancied between it and the little 

 fish. The name, however, is not the only one in use in England : 



'The Triglopsis tliojiipsoiii of the Great Lakes, often associated with the 

 Cottincs or otherwise misplaced, is a typical Myoxocephaline, very closely 

 related to the common Oncocottus quadricornis {Cottus quadricornis of most 

 authors). The present author indicated this relationship as early as 1862 

 (Proc. Acad. Nat. Sc. Phila., p. 13). 



