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to the floor of the cranial cavity. Through the aperture and into the space roofed by this membrane, 

 certain of the eye muscles extend, the space thus being a perfectly normal mvodome. 



Of the Cottidae, said by Cope to be without a myodome, I have described it in the present 

 work, well developed, in Cottus octodecimospinosus; and Gill ('91b) gives as one of the characteristics 

 of his family Cottoidea, , .Myodome more or less developed". 



Of the Rhamphocottidae, I have no specimens, but the Cottidae having a myodome, certainly 

 well developed in some species, it must surely be also found in the closely related Rhamphocottidae. 



In Gonorhynchus greyi, Ridewood ('05b) says there is a myodome. 



Of the entire list of fishes said to be without a myodome, all of the individual species mentioned, 

 excepting only Caularchus, Callionymus, Fistularia, Cyclothone, Silurus and the eel, are thus shown 

 to have that canal; while of the several f amilies in which the canal is said to be absent, some one or 

 more members of each family, or of a closely related subfamily, are also shown to have it, excepting 

 onlv the Cyclopteroidea, Cromeriidae, Gobiidae, Gobiesocidae, Stomiatidae, Batrachididae and 

 Comephoridae. Of the Cyclopteroidea, Cromeriidae, Gobiesocidae, Stomiatidae, Batrachididae and 

 Comephoridae, I have no specimens; neither have I of Caularchus, Callionymus, Fistularia or Cyclo- 

 thone. These fishes must accordingly be left out of consideration. Of Fistularia, it may, however, 

 be stated that Swinnerton shows a myodome in Gasterosteus, and that I find a well-developed myodome 

 in Centriscus, both of which fishes belong with Fistularia to the Hemibranchii. Of the Siluridae, 

 Muraenidae, and Gobiidae, I have specimens and they can now be considered. 



In Conger conger of the Muraenidae, there is, at the hind end of the orbit, a small median 

 transverse shelf of bone which projects forward slightly above the parasphenoid. The optic nerves 

 leave the cranial cavity along the dorsal surface of this shelf, and beneath it, between it and 

 the parasphenoid, the recti muscles have their origins. The bones of the skull are here all so 

 firmly ankylosed in my specimens that I can not with certainty identify them, but the shelf of bone 

 must certainly be either a basisphenoid, a proötic bridge similar to the bridge of Gadus, or a trans- 

 verse ridge of the parasphenoid, as in Dactylopterus. And in either case the little space between 

 the bone and the body of the parasphenoid would be a perfectly normal but very much reduced 

 myodome. In a series of sections that I have of a young Conger, the recti muscles all seem to 

 arise from a delicate median membrane, which lies partly beneath and partly anterior to the shelf 

 of bone, each muscle arising directly 1 opposite its fellow of the opposite side; no one of the muscles, 

 apparently, having its origin either on the shelf or on the parasphenoid bone. 



In a single small specimen of Gobius cruentatus that I hare been able to obtain, the arrange- 

 ment seems to be exactly similar to that in Dactylopterus. The proötic has a narrow orbital surface 

 which lies at a slight angle to that part of the bone that lies immediately posterior to it and that 

 forms the uniformly thin floor of this part of the cranial cavity. The narrow orbital surfaces of the 

 bones of opposite sides are separated by a wide median interval, and the ventral part of this interval 

 is filled by a transverse ridge on the dorsal surface of the parasphenoid. This ridge on the para- 

 sphenoid has the same antero-dorsal inclination as the orbital surfaces of the proötics, and forms 

 the hind wall of a small pocket which lies at the hind end of the orbits, and recalls both the myodomic 

 pocket of Gadus, and the myodome of Dactylopterus. 



Of Silurus I can find no description that is of value in this connection. But McMurrich's 

 ('84) descriptions of Ameiurus catus (nebulosus) are of value, and, as I have a few specimens of this 

 fish, it can be described. Short reference must, however, first be made to Sagemehl's descriptions of 



