SYSTEMATIC ACCOUNT 165 



which extend on to the dorsal surfaces of their respective somites. As in the anterior somites, coxal 

 plates also extend from the inner borders of the joints to the mid-ventral line; those of the last 

 segment in species of Glyptonotiis are fused together (Text-fig. 1 1 a). 



According to Richardson (1904, pp. 39-40) Symmius caudatus has 'epimera present and developed 

 on only the last three segments of the thorax as in Glyptonotiis Eights, the epimera of the three anterior 

 segments being perfectly united with the segments and with no trace of suture lines '. If this statement 

 were true, there would be an important morphological difference between these two genera, but an 

 examination of the British Museum specimen shows that this statement is incorrect, the form of the 

 coxa is the same in both genera. 



Genus Glyptonotus Eights, 1852 



Glyptonotus antarcticus Eights, 1852 (Plate IX, figs. 1-5; Text-fig. iia-d) 



G. antarcticus Eights, 1852, pp. 331-4, 2 pis.; Miers, 1881, p. 11; Pfeffer, 1887, pp. 115-25, pi. 2, fig. 7; pi. vi, 



figs. 13-27; Tait, 1917, p. 246, 22 text-figures; Collinge, 1918, p. 65, pis. i, 2, figs. 1-12; Tattersall, 1921, 



pp. 232-3; Calabrese, 1931, pp. 323-6, 2 text-figures; Monod, 1931, p. 27; Nordenstam, 1933, pp. 104 and no. 



G. antarcticus var. acutiis Tattersall, 1921, pp. 233-5, pl- 'x> ^g^- 3. 4; Pesta, 1928, pp. 78 and 81 ; Calabrese, 1931, 



pp. 323-6; Nordenstam, 1933, p. 104. 

 G. acutus Richardson, 1906, p. 10, pi. i, figs. 2-4; Hodgson, 1910, p. 45, pi. vii; Richardson, 1913, p. 17; Vanhoffen, 

 1914, p. 527. 

 Occurrence. St. 141, 29. xii, 26, East Cumberland Bay, South Georgia, 17-27 m., i J and i $ (non-breeding). 

 Jan. 1927, Borge Bay, South Orkneys, fish trap, i S- St. 164: 18. ii. 27, East end of Normanna Strait, South Orkneys, 

 24-36 m., I cJ, 2 immature. St. 178: 9-1 1. iii. 27, Melchior Harbour, Schollaert Channel, Palmer Archipelago, 

 17 m., I (J. 1927, Admiralty Bay, King George Island, South Shetlands, brought up on anchor chain, i S- 28. x. 28, 

 King Edward's Point, South Georgia, picked up on beach, i S- St. 366: 6. iii. 20, 4 cables south of Cook Island, 

 South Sandwich Islands, 155-322 m., i immature specimen; 77-152 m., 3 immature and i immature S- St. 370: 

 10. iii. 30, 2 miles north-east of Bristol Island, South Sandwich Islands, 80-18 m., i ? (non-breeding). St. 371 

 14. iii. 30, I mile east of Montagu Island, South Sandwich Islands, 99-161 m., 2 immature specimens, 99-161 m. : 

 ? (breeding), i ^ (non-breeding) and 2 S3- i?- ii- 31. Leith Harbour, South Georgia, 5 m., from fish stomach, 

 probably from Notothenia rossii, i incomplete S- St. 1489: 17. i. 35, Port Lockroy, Palmer Archipelago, found on 

 motor-boat at anchor. St. 1652: 23.1.36, 75° 56-21' S., 178° 35-5' W., 567 m., i? (non-breeding). St. 1941: 

 29. xii. 36, Leith Harbour, South Georgia, 38 m., 2 young specimens. St. MS 25 : 13. iv. 25, East Cumberland Bay, 

 South Georgia, 36 m., i immature S- 



Remarks. The only additional points of interest concerning the anatomy of this species have 

 already been dealt with in the general discussion on the characters of the suborder Valvifera and the 

 subfamily Glyptonotinae (pp. 148-164). 



The separation of G. acutus, even as a variety from G. antarcticus, seems to be a matter of great 

 difficulty, if a series of specimens is examined; for it is almost impossible to draw a dividing hne 

 between the types, the grading is so complete. 



The species G. acutus was formed by Richardson (1906) to contain a type which differed from 

 G. antarcticus only in proportion. According to Richardson the length of the body of G. antarcticus 

 is less than twice as long as it is broad, and the terminal segment is broader than long; on the other 

 hand, the length of G. acutus is two and a half times its breadth, and the terminal segment is longer 

 than broad (10-6 mm.). Richardson obtained the proportions given for G. antarcticus from the 

 published descriptions and figures of Eights (1852), Miers (1881) and Pfeffer (1887); Miers's descrip- 

 tion is based on that of Eights, and he gives the size of a specimen as length 90 mm., breadth 45 mm., 

 a ratio of 2:1 ; a similar ratio is obtained by measuring Pfeffer's figures. 



Measurements taken from Richardson's specimen of G. acutus show a ratio of length to breadth of 2- 1 : i 

 and not 2-5:1, so that the actual difference in the length: breadth ratio of the two species is very small. 



