DEVONIAN FISHES OF IOWA 91 



We may now return, finally, to a consideration of one or two 

 doubtful matters. Neither on the dorsal nor ventral surface of 

 the head region are there any certain indications of olfactory 

 openings. It has been suggested by Smith Woodward, however, 

 that the rounded notch occurring at the external angles of the 

 maxillary plates in Pterichthys and Bothriolepis may indicate 

 the opening of a nasal sac, and it is indeed difficult to conceive 

 what other function it could have subserved. Professor Patten 

 offers no explanation of the notches in question, and is forced to 

 conclude from the absence of any other orifices that the orbital 

 and nasal openings were confluent. The pineal plate and the 

 T-shaped one in front of it, alongside of which the olfactory 

 nerves are supposed to have passed according to Patten's con- 

 jecture, were capable (in this author's opinion) of sliding back 

 and forth at the same time as the sclero tics, the eyes and olfac- 

 tory pits being opened by one set of movements, and closed by 

 a reverse set. It is to be regretted that there are no means of 

 proving whether or not this ingenious contrivance ever existed. 

 Eeal or imaginary, it had, however, this rather awkward defect : 

 the creature possessing it could not smell with its eyes shut. 

 Nature is not usually so economical that vertebrate organisms 

 have the sense of sight and the sense of smell localized within 

 a single opening. And the invariable position of the nasal open- 

 ings in chordates is inferior, never on the dorsal aspect of the 

 head. 



As for the peculiar markings described by the Dartmouth 

 author (loc. cit., 1905) as "broad membranous folds, of unknown 

 function, around the posterior end of the cephalic buckler", these 

 are probably to be interpreted as impressions of the extruded 

 viscera. It is stated in the same communication that certain 

 specimens disclose the shape of the brain-chamber, an announce- 

 ment which bids fair to yield interesting information. 



Formation and locality. Upper Devonian; Scaumenac Bay, 

 Province of Quebec, Canada. 



