xxni ACANTHOPTERYGII 691 



DIVISION VI DISCOCEPHALI. 



Highly aberrant Acanthopterygians with the anterior dorsal 

 fin modified into a suctorial, transversely laminated oval disk 1 

 on the head, the skull being very much flattened and with simple 

 basis cranii. The pectoral rays are inserted on the small, per- 

 forate, scapula and on four hour-glass-shaped pterygials, three 

 of which are in contact with the coracoid. Ventrals thoracic. 



Fam. 1. Echeneididae. Maxillary slender, adnate to the 

 upper surface of the praemaxillary ; suborbital arch slender. 

 Pectoral fin inserted high up ; supraclavicle much reduced ; 

 ventral fin with one spine and five soft rays. Body elongate 

 and covered with small scales ; soft dorsal and anal fins elongate 

 and opposed to each other. All the praecaudal vertebrae with 

 very strong parapophyses, the anterior with diapophyses as well ; 

 ribs and epipleurals nearly equally developed, both inserted at 

 the extremity of the parapophyses. 



FIG. 421. Remora brachyptera. (After Goode.) x J. 



Iii spite of a superficial external resemblance to the genus 

 Elacate, the Sucking-Fish bear certainly no affinity to that genus 

 nor to other Scombriformes, as first observed by Gill. They are 

 probably derived from Perciformes, but from which family it is 

 impossible to suggest. Three genera may be distinguished : 

 Opisthomyzon, from the Upper Eocene of Switzerland, with a 

 very small suctorial disk and 23 or 24 vertebrae; Eclieneis, with 

 large disk and 30 vertebrae; and Remora, distinguished from the 

 second by a shorter body with only 27 vertebrae. These re- 

 markable fishes, of which about 10 species are distinguished, are 

 distributed all over the tropical and warm seas, and exceptionally 

 carried as far north as the south coast of England. They feed 

 on other fishes, and attach themselves by means of their cephalic 



1 For the theories on the formation of the disk, cf. R. Storms, Ann. Mag. Nat. 

 Hist. (6), ii. 1888, p. 67. 



