160 Edward Phelps Allis jr., 



In Menidia (No. 17) the arrangement is as in Scomber, the poste- 

 rior squamosal organ being post-preopercular in position and being 

 innervated by an anterior branch of the suprateraporal branch of the 

 nervus lineae lateralis. 



Ameiurus melas (No. 18) differs from Scomber and Menidia, and 

 agrees with Amia and Polypterus, in that the posterior squamosal 

 organ is innervated by a supratemporal branch of the glossopharyn- 

 geus, which nerve also innervates a middle head line of pit-organs 

 "consisting usually of two large pit organs on each side forming a 

 aransverse line across the top of the head a very short distance 

 caudad of the union of the opercular canal with the main canal in 

 the squamosal". In this fish Herrick says there is no vestige of a 

 supratemporal commissure; but there is a small post-squamosal ossicle, 

 containing a sense-organ, which Herrick considers as probably corres- 

 ponding to "the lateral extrascapular or supratemporal bone" of Po- 

 lypterus, Gradus, and certain other fishes. 



In Gadus (No. 11) the arrangement is somewhat different. In this 

 fish the preopercular canal does not join the main horizontal canal, but 

 its dorsal end lies practically opposite the hind end of the otic sec- 

 tion of that canal; thus here agreeing with the several other fishes 

 above referred to. It differs however radically from those fishes in 

 that the squamosal does not extend posterior to tliis point and there 

 lodge a sense organ innervated by a post-auditory nerve. In Gadus 

 a so-called supratemporal ossicle lies immediately behind the otic sec- 

 tion of the main horizontal canal, and it is said to not be directly 

 related to a lateral sensory organ. Such an organ, called by Cole 

 organ No. 3 of the lateral canal, lies, however, between this little os- 

 sicle and the adjacent supratemporal ossicle, and as this latter ossicle 

 lodges organ No. 2 of Cole's nomenclature, the first mentioned ossicle 

 can be assumed to be genetically related to organ No. 3. This lattei- 

 organ is innervated by an anterior branch of the supratemporal branch 

 of the nervus lineae lateralis, and would accordingly seem to be the 

 homologue of the organ similarly innervated in Scomber, which organ 

 seems to be the homologue of the glossopharyngeal organ of Amia. 

 The separate ossicle of Gadus would then be the homologue of a 



