Families of Ttlcostean Fishes. 183 



This division embraces three families oiilj : — 



A spinous dorsal fin ; anal spines detached from 



the soft portion ; a ventral spine ; gills three 



and a half, three slits between them 1. Zeiclce. 



Dorsal and anal spines few, continuous with the soft 



raj'^s ; a ventral spine 2. Amphistiidm f. 



No spines ; cranium twisted in front, with the two 



orbits on one side ; gills four, a slit behind the 



fourth 3. Pleuronectidce. 



Division IV. Kurtiformes. 



No bony stay for the prseopercle. Dorsal spines feeble, 

 few. Scapula absent, the coracoid supporting four small 

 pterygials. Ventral tins thoracic. 



A single family, Kurticke. 



Division V. Gobiiformes. 



No bony stay for the praoperculum. Basis cranii simple. 

 S[)inous dorsal, if present, formed of few, flexible rays. 

 None of the epipleural bones attached to the centra of the 

 vertebra in the praicaudal region. Scapula and coracoid 

 more or less reduced or even vestigial ; pterygials large, 

 4 or 5 in number, forming together a thin plate which is iu 

 contact vvitli or narrowly separated from the clavicle; one or 

 two of the pterygials in contact with the coracoid. Ventral 

 fins thoracic. 



The Gobiidce., which alone constitute this division, are not 

 very remote from the Perciformes and may have evolved out 

 of a type not very different from the Percidaj. 



Division VI. Discocepiiali. 



Highly aberiant Acanthopterygians with the anterior 

 dorsal fin modified into a suctorial, transversely laminated 

 oval disk on the head, the skull being very much flattened 

 and with simple basis cranii. The pectoral rays are inserted 

 on the small, perforate, scapula and on four hourglass-shaped 

 pterygials, tliree of which are in contact with the coracoid. 

 Ventral fins thoracic. 



A single family, Echeneididm. 



In spite of a superficial external resemblance to the genus 

 Elacaie, the sucking-fish, as first observed by Gill,* bear 

 certainly no affinity to that genus nor to other Scombri- 

 formes. They ai'e probably derived from Perciformes, but 

 from which family it is impossible to suggest. 



''0}yn. ^fz^ rU 



