440 FISHES OF THE FIRTH OF FORTH. 



it generally remains all the year in the fresh water, as spe- 

 cimens ean be obtained in the Thames all the year through. 

 It has been conjectured by some, that this species, as well 

 as the last described, had both sexes united in the same in- 

 dividual, but this is now satisfactorily proved not to be 

 the case. They spawn in the month of May, and are in the 

 best condition for the table from October to March. 



Petromyzon Planeri.* — Planer's Lamprey. 



Specific Characters. — Dorsal fins contiguous, second dorsal uniting 

 with the caudal. 



Description. — From a specimen five inches in length. In form it 

 very much resembles the Lampern, but rather thicker in proportion 

 to its length ; head bending slightly, falling obliquely from the sum- 

 mit ; mouth of an oval form, circular when expanded ; placed at the 

 extremity ; lip thickly fringed, furnished on the inner surface with a 

 number of small, yellowish tooth-like projections with pointed sum- 

 mits ; a large semicircular tooth below with seven small sharp points 

 directed forwards; on the roof of the mouth one tooth with two remote 

 points directed downwards. Eyes rather large of a rounded form, 

 situated about half-way between the tip of the snout and the fourth 

 branchial opening ; head indistinct, a small nasal orifice placed on 

 the summit a little in advance of the eyes. Branchial openings seven 

 on each side of the neck, arranged in a line commencing at a short 

 distance behind the lower portion of the eye, taking an oblique di- 

 rection backwards and slightly downwards. Colour of the back and 

 sides dusky blue ; belly of a dirty silvery- white ; fins light dusky 

 grey. First dorsal fin commencing mid-way between the tip of the 

 snout and the end of the tail, somewhat of a semicircular form, termi- 

 nating by uniting with the second dorsal ; its height about one-third 

 the length of its base. Second 7 dorsal about twiee the size.of the first 

 and similar in shape, but reaching its greatest height rather more 

 suddenly. Caudal contiguous with the termination of the second 

 dorsal ; cut obliquely both above and below, and ending in an obtuse 

 point ; body marked throughout the whole length with a number of 

 fine lines passing from above downwards. Vent situated immediately 

 under the middle of the anterior half of the second dorsal, and fur- 

 nished with a prominent fleshy tubercle in front ; skin everywhere 

 smooth. 



* Peli omyzon planeri, Y arr., Jen,, Cuv. Planer's Lamprey. Fringed- 

 lippcd Lamprey. 



