3 8 DISCOVERY REPORTS 



Standard length 54 mm. Diaphus agassizii Gilbert 



This individual contained a well-developed swimbladder measuring about 7 mm. in length. 



Notolychnus valdiviae (Brauer) (Text-fig. 2 id) 



St. 1586, 02 39-4' N., 50 46-4' E., 2. v. 35, TYFB i6so-95o(-o) m. B.M. Reg. no. 1948.5. 14. 310-25. Standard 

 length 19 mm. (1-5 x 075 mm.). 



As in other myctophids, the swimbladder originates over the stomach, but is so small that it does 

 not extend beyond this organ. Except for the roof, the gas-gland covers the entire inner surface of 

 the sac. The three retia mirabilia, which have a length of about 1-75 mm., run backwards and up- 

 wards along the right lateral wall of the stomach and enter the anterior part of the swimbladder floor. 



In another fish (standard length 19-5 mm.) from St. 1586 the swimbladder had a length of nearly 

 2-5 mm. Though the sac of both fishes was somewhat relaxed, it would seem that the swimbladder of 

 this species is reduced in size. 



Lampadena chavesi Collett (Text-fig. 21A-C) 

 Position, 5i°23'N., n°47'W. B.M. Reg. no. 1911.2.8. 1. Standard length 75 mm. (9-5 x 3-5 mm.). 



The swimbladder of this lantern fish arises above the forepart of the stomach and extends down 

 the remainder of the body-cavity. The three retia mirabilia enter the right anterior part of the sac 

 and run backwards to supply a gas-gland covering the forward half of the swimbladder floor. 



Each rete has an individual length. The innermost one, with a span of about 2-5 mm. supplies the 

 foremost lobe of the gas-gland, while the next lobe is fed by the middle complex, which is 4-5 mm. in 

 extent. The outermost rete is the largest (about 5-75 mm.) and runs to the posterior lobe of the gland. 



Alongside the retia, forming an anterior extension of the swimbladder, is a conical projection 

 (presumably the oval) that is well supplied with blood-vessels. 



Lampanyctus giintheri Goode & Bean (Text-fig. 22 a) 



St. 710, 21 45' S., 39° 50' W., 26. x. 31, TYFB, 294^0) m. B.M. Reg. no. 1948.5. 14. 534-56. Standard length 

 53 mm. (9-5 x 2-5 mm.). 



In this species the swimbladder is a thin-walled sac occupying about four-fifths the span of the body- 

 cavity. The rounded forward extremity lies just behind a vertical line drawn through the base of the 

 pectoral fins. 



The three retia mirabilia lie under the forepart of the swimbladder and extend backward to the 

 medially situated gas-gland. Each rete is almost 3 mm. in length, while the gas-gland, which invests 

 the floor and side walls, has a length of 2-3 mm. The artery and vein supplying the retia mirabilia 

 come from the dorsal aorta and hepatic portal system respectively. 



Centred above the middle point of the retia and on the left side of the swimbladder, the oval 

 appears as a thin-walled blister, 1 -8 mm. in width. This opens into the main cavity through an oval 

 aperture situated in the side wall just above the retia. The walls of the oval are richly supplied with 

 capillaries and larger vessels. 



Lampanyctus alatus Goode & Bean (Text-fig. 22 b) 



St. 2057, 12 09' S., 04 28-2' W., 29. iv. 37, N 450 B, i450-70o(-o) m. B.M. Reg. no. 1948.5. 14. Standard 

 length 57-0 mm. (9-0 x 2-5 mm.). 



This species has a capacious swimbladder extending down about two-thirds the length of the 

 body-cavity. The walls are rather thin but well strengthened, with collagen fibres. 



In side view the swimbladder has a gradually tapering forward section, the floor of which is 



