— 156 — 



Having left the pterotic, the caual traverses a groove in the lateral edge of thc lateral extrascapular, 

 but no organ could be found related to that bone. The canal tlien traverses in succession the supra- 

 scapular and supraclavicular, in each of which bones there is a single organ. 



The main infraorbital canal of Peristedion thus differs from that of Trigla in that the pterotic 

 lodges but one organ innervated by the oticus lateralis, instead of two, without intervening primary 

 tube; and in that there is no apparent organ related to the lateral extrascapular. 



The supratemporal canal lodges, as in all the other fishes of the group, two organs, one lying 

 in the lateral extrascapular and the other in the parieto-extrascapular. 



The supraorbital canal agrees strictly with the canal in Scorpaena and Trigla, but between 

 the nasal and frontal bones the canal is enclosed, for a relatively long distance, in the dermal portion 

 of the mesethmoid bone ; this section of canal lodging no sense organ. The nasal lodges a single sensc 

 organ, and the frontal five organs, the fourth and fifth organs of the line lying close together without 

 intervening primary tube, as in Scorpaena and Trigla. The fourth primary tubes of opposite sides 

 unite in the middle line to form a frontal commissure. 



The preoperculo-mandibular canal contains ten organs, instead of eleven as in Trigla, three 

 of these organs lying in the dentary, one in the articular and six in the preopercular. After leaving 

 the dorsal end of the preopercular the canal traverses a short suprapreopercular bone, without related 

 organ, to reach and anastomose with the main infraorbital canal between the two organs in the pterotic. 



The primary tubes, in Peristedion, do not branch repeatedly after entering the dermal tissues, 

 as they do in Scorpaena, Cottus and Trigla. Certain of the tubes, however, apparently undergo one 

 or two subdivisions, and the mouths of all of them become enlarged and most of them are closed 

 by drum-head-hke membranes perforated by several small openings. 



IV. Dacty lopterus volitans. 

 1. SKULL. 



Of this fish I have had five specimens, ranging from 1.3 cm to 41 cm in length, and a number 

 of specimens ranging from 5 cm to 10 cm in length. A single one of these specimens, 35 cm in 

 length, was the only one I had during the earlier periods of the investigation, the other large specimens 

 being later obtained, one at a time. The study of the cranial bones presenting peculiar difficulties, 

 all of these large specimens were successively sacrificed to it, the soft parts thus not being examined 

 in any of the adults. When the small specimens were later obtained, several of them were sectioned. 

 but, because of the character of the bones and other tissues, only one comparatively good series of 

 sections was obtained. This series alone served for the study of the nerves. 



Grill ('90, p. 245) says, of the skull of Dactylopterus, that ,,its upper surface is derived partly 

 from a dermal ossification which is incongruous with the true bones". Just what this statement 

 means is not clear, for the bones in this fish differ in no way, exceptiug in degree, from those in Trigla 

 and Peristedion. As in these two latter fishes, all of the primary bones that come to the level of, 

 and form part of the dorsal surface of the skull of Dactylopterus have an external surface exactly 

 similar to that of the adjoining and purely dermal bones; and the sections of young Dactylopterus 



