CLELAKD ON THE ANATOMY OF THE SnORT SUN-FISH. ISl 



by the olfactory nerves, which almost immediately afterwards pierce 

 the skin to supply the extremely minute nostrils, situated about an 

 inch in front of the eyes. 



The osseous texture of the bones behind the trigeminal nerve 

 extends inwards to the cranial cavity. Both on the external and 

 internal aspect they have regular edges which come almost in contact, 

 but in the thickness of the wall there is a greater quantity of 

 persistent cartilage than bone. 



On inspecting the interior of the cranium, I find, strange to say, 

 that there are no otoliths at all, and that each ear has only two 

 semicircular canals, which ai'e, however, of great length.* The 

 small vestibulary sacs of opposite sides are united by a slender tube. 

 Thus it appears that, of the three principal organs of special sense 

 in the sun-fish, two are very imperfectly developed, while the re- 

 maining one — the eye — is very large, its globe being, in the specimen 

 described, more than an inch and a half in diameter. 



Concerning the face bones little need be said. On account of 

 the small size and projecting position of the jaws, the palatals and 

 pterygoids are very short, while the tympanic series (of Owen) and 

 the preoperculum are very elongated. The palatals send backwards 

 long processes on the sides of the basisphenoid, which supj)ort them 

 against the pressure of the maxillaries. The epitympanic articulates 

 not only with the mastoid and postfrontal, but also with the 

 alisphenoid. 



The bones of the opercular range are three in number. "Wellen- 

 bergh could find only two, and contradicts Meckel who describes 

 three ; but Meckel is right. The operculum is very small ; its 

 breadth does not exceed that of the joint on which it moves. The 

 interoperculum is slightly dilated above to lay hold of tlie operculum, 

 and is prolonged down as a linear process, which is continued into 

 a ligament which, concealed by the preoperculum, is directed toward 

 the angle of the lower jaw. The suboperculum is a mere linear 

 ossification contained in this ligament. 



The shoulder-girdle is very large in proportion to the head. There 

 is no suprascapular bone. The elongated scapula articulates im- 

 mediately with the mastoid. To the lower half of the coracoid is 

 attached the " ulna ;" and against the upper border of this abuts a 

 roAv of small bones which support the pectoral fin. These bones are 

 four in number ; they lie in a row, are similarly related to the fin, 

 and are very like each other in general appearance, especially the 

 most anterior two of them. Tet, the first of them is related to the 

 coracoid and " ulna " exactly as is the " radius " in the cod, and, like 



* Professor Goodsir has pointed out to me that the ear in Petromyzon has like- 

 wise only two semicircular canals. In Bddlostoma and Mya-inc the membranous 

 vestibule is reduced to a ring. In none of these genera are any otoliths found. 

 See Miiller " Ucbcr den eigenth. Bau des Gchbrorganes bei den Cyclostonien.' 

 Berlin, 1838. 



