172 ACANTHOPTERYGII. 



Genus 3-. — Crystallogobius, Gill. 

 Gobiosoma (part) Giinther : Latrunculodes, Collett. 



Branchiostegals seven : pseudobranchiai present. Body elongated and compressed. 

 Teeth only distinctly present in the males and in a single row, with two strong 

 canines in the lower jaw. Gill openings wide. Two separate dorsal fins, the first 

 composed of two spines, the second with a moderate number of rays (19-20) : anal 

 almost similar to the second dorsal. Ventrals united forming a 'disc. Scales absent. 

 Air-bladder present. 



Geographical distribution. — Coasts of Norway and Sweden, also the west coast 

 of Scotland off Banffshire, so probably exists in intermediate localities, but has 

 escaped detection due to its small size and being mistaken for Aphia pellucida. 

 Most that is known of this fish is due to the labours of Professor Collett, from 

 whom the greater portion of the following remarks are taken. 



Crystallogobius Nilssonii, Plate LIII, Fig. 4 (-§■ male). 



Gobius Nilssonii, Dub. and Kor. Vet. Akad. Handl. Stockh. 1844, p. 53, t. ii, 

 f. 3 ; Nilss. Skand. Faun, iv, p. 227; Life of Edward pp. 375, 427. 



Gobius linearis, Dub. and Kor. Ofver. Vet. Akad. Handl. 1845, i, p. 111. 



Gobiosoma Nilssonii, Giinther, Catal. iii, 1861, p. 86. 



Crystallogobius Nilssonii, Gill, Proc. Acad. Nat. Sc. Phil. 1863, p. 269 ; Collett, 

 Pro. Zool. Soc. 1878, p. 331. 



Latrunculus Nilssonii, Collett, Forh. Vid. Selsk. Christ. 1872, p. 10. 



Latrunculodes Nilssonii, Collett, 1. c. 1874, p. 151. 



B. vii, D. 2/19-20, P. 30-31, V. 1/5, A. 21, C. 14-15, Vert. 29. 



Length of head 4-*- to 5^-, of caudal fin 7\, height of body 7 to 8£ in the total 

 length. Eye — lateral, diameter 1/4 of the length of the head, 1 diameter 

 apart in the females, a little more in the males, and 1 diameter from the end of 

 the snout. The heads in adult males are thickened and the snout short : the cleft 

 of the mouth deep, while the end of the mandibles are bent upwards and received 

 into an emargination in the upper jaw. In the young males the head is more 

 pointed, almost as in the females, in which the jaws- are short, straight, and 

 toothless. In adult males the maxilla extends backwards to beneath the hind 

 edge of the eye. Teeth — These are not changed during the breeding season as 

 observed in Aphia. The males at this period have 13 to 14 closely placed, small, 

 acute, and pointed teeth in a single row in the premaxillaries, while on the projecting 

 square extremity of the mandibles there is externally a canine at each angle and a 

 single row of eight fine-pointed teeth extending between the canines. Fins — The 

 first dorsal fin in the male commences over the base of the pectoral fin, and 

 consists of two rays which come to a fine termination, but are not continued 

 beyond the membrane, which extends as far as the base of the second dorsal fin. 

 The anal is similar to the second dorsal, both consisting of short and undivided 

 rays, except the last which is sometimes divided. Pectoral, with a broad base, 

 and well developed, its central 12 or 14 rays are branched. Caudal square or 

 slightly emarginate, with 9 or 10 short rays on either side of its base. Ventral 

 reaches half way to the vent, its inner rays shorter than its outer ones. The vent 

 is situated midway between the end of the snout and the root of the caudal fin. 

 The angular insertions of the muscles along the side of the body are well marked, 

 being about 27 in number. Colours — Almost transparent, with a light bluish 

 tinge : a dark spot at the end of the lower jaw. A small black spot at the root 

 of each dorsal and anal ray, those along the dorsal being sometimes wanting in 

 the female. 



Habits. — It would seem to inhabit somewhat deep water, and probably rests at 



