SUCKER-FISHES. 



407 



trunk vertebrae are extremely slender, the third alone being nearly as long as the 

 whole caudal portion ; while in the latter all the vertebree are very short. In a 

 fossil state the tortoise-fishes are represented in the middle Eocene of Monte Bolca ; 

 and it may be mentioned here that in the preceding family the genera Fistularia 

 and Aulostoma occur not only in those deposits, but likewise in the lower Eocene 

 of Switzerland ; and Auliscops has been recorded from the Eocene of Sumatra, 

 and two extinct generic types have been described from the Monte Bolca beds. 



The Sucker-Fishes, — Family Gobioesocidjz. 



The small fish (Lepadogaster bimaculatus), of which three examples are 

 shown in the annexed illustration, is one of three British representatives of a genus 

 belonging to a small family which constitutes a sectional group by itself. Long 



two-spotted sucker-fish (nat. size). 



confounded with the lump-suckers, which they resemble in having an adhesive 

 disc on the under surface of the body, the sucker-fish differ from that group, not 

 only in the structure of that disc, but likewise in several other respects. They have 

 no spinous dorsal fin ; the soft dorsal and anal are short or of medium length, and 

 situated far back, at the root of the tail ; the pelvic fins are almost jugal in 

 position, and have the adhesive disc placed between them; while the body is 

 covered with a naked skin. Whereas in the lump-suckers the pelvic fins are close 

 together, and actually form the base of the sucking disc, in the present family 

 they are widely separated from each other, and only enter into the composition 

 of a portion of the margin of the adhesive apparatus, which is completed by a 

 cartilaginous expansion of the bones of the pectoral girdle. In size the ovoid disc 

 is relatively large, its length being sometimes as much as one-third that of the 

 whole fish, and it is divided into an anterior and a posterior moiety, of which the 

 second may or may not have a free front margin. All these fishes are littoral 

 forms of small size, ranging over both temperate zones, where they are more 



