368 THE RELATIONS OF CY».LOPTEROIDEA GILL. 



iSuhorhitals well developed, completely covered by the skin, but on 

 dissection tbe third is found to be well developed, crossing the cheek 

 and meeting the inner margin of the preopercnlnm. 



Operculum apparatus fully developed ; Operculum thin, with its upper 

 and posterior portions thin but fortified by upper and lower ribs; radiat- 

 ing from its articular condyle are several less developed intermediate 

 rays of ossification ; Subopoxtilum with a slender portion under and be- 

 low the operculum, and a larger, wider i^ortiou below the preoperculum ; 

 Interoperculum mostly slender, but with an expanded posterior portion. 



Preoperculum with two limbs, the upper vertical and somewhat ex- 

 panded downward, and the lower oblique, tending to horizontal, and 

 witli a laminar inferior or external margin. 



Br anchiotr ernes restricted to the side^ ; the branchiostegal membrane 

 more or less joined to the isthmus but with a free marginal told. 



Branchiostegal rays six on each side. 



i)orsa/is generally double; the anterior variously developed, in the 

 typical forms being small and mostly concealed in the grooves formed 

 by the upraised skin and prominent tubercles of the back, in some well 

 developed and conspicuous, in others obsolete or suppressed; the soft 

 dorsal is behind on tbe posterior portion of the body and has about eight 

 to twelve rays. 



Analis simihir to the second dorsal and opposite it. 



Caudalis with about nine to eleven well-developed rays and few small 

 rays above and below. 



Feciorales with very broad bases procurrent below, and with numerous 

 unbranched rays connected by continuous membrane. 



Veniralis modified to form a subcircular or oval suctorial disk ; the 

 rays have the basal processes extending mesiad, appressed to the pel- 

 vic bones, and immovable; tl>.ero are six in number on each side, none 

 of which are articulated, they being mostly converted into imperfect 

 bony tissue like the rest of the skeleton. 



Branchiw four, with the slit behind the last arch obsolete or sup- 

 pressed; gill-rakers developed as slight tubercles. 



SKELETON. 



The skeleton of Gijclopterus lumpus has been noticed by Dr. Giinther 

 (Cat. Fishes B. M. v. 3 pp. 156, 157), and inasmuch as his observations 

 disagree with the characters here assigned to the including superfamily 

 and family, the chief discrepancies may be mentioned. 



The bones of Cijdopierus are distiugnislied by tbe small quantity of calcareous salts 

 deposited in them : the latter form thin lam<^ll£B in each of the bones, and the inter- 

 spaces between these layers are filled with a soft gelatinous substance which is soon 

 dried up, so that the bones shrink together to a shapeless mass. In a fish with the 

 bones so incompletely ossified and semimembrauaceous, it is often impossible to find 

 the sutures between them. 



The chondrocranium is in great part persistent, but covered in by the 

 bones, which are superficial and can be peeled off, the cartilage bones 



