ENTOMOSTRACA OF THE SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 321 



tioned they are elongated. The length of the specimen represented by the drawing 

 (fig. 1) is 0'62 mm. (^ of an inch). 



Antennules tolerably slender, and composed of five joints, the penultimate being 

 very small. Antennae small ; outer ramus wanting. 



Mandibles and other mouth-organs nearly as in Laophontodes typicus ; the second 

 maxillipeds are slender, and are each provided with a long and slender terminal claw. 



The first pair of thoracic legs resemble those of the species mentioned, and the 

 next three pairs are also similar to those in the same species. In the second, third, and 

 fourth pairs, the inner ramus is short, two-jointed, and very slender, the first joint being 

 very small ; the inner ramus of the pair is, however, proportionally rather more 

 elongated than the others. 



In the fifth pair, the basal joint is rather longer than the second one, and both are 

 provided with a few setse. 



Caudal rami short, scarcely longer than the last segment of the abdomen. 



Habitat. Scotia Bay, South Orkneys, in some siftings from dredged material 

 collected in June 1903; Station 325, 60 43' 42" S., 44 38' 33" W. 



Remarks. The form described above may be at once recognised from any previously 

 described species by its short caudal rami ; it is also rather more slender and elongated 

 than any of those previously described. 



Its occurrence in the Scotia collections is a further indication of, in some respects, 

 the close similarity between the Copepod fauna of the Antarctic and that of our 

 northern seas. G. 0. SARS has recorded three species of Laophontodes from the coasts 

 of Norway, and two of them also occur in British waters. Moreover, one of these 

 northern forms (Laophontodes typicus) was also collected by Dr BRUCE as far north as 

 Franz Josef Land. All the three northern species are provided with long caudal 

 rami, and are thus readily distinguished from the one now described. This species is 

 named in compliment to Mr THOMAS B. WHITSON, a member of Committee and 

 Honorary Accountant to the Expedition. 



Fam. CLETODIDJI;. 

 Genus Orthopsyllus, Brady & Robertson, 1873. 



Orthopsyllus linearis (Glaus). (PI. IX. figs. 10-22.) 



1866, Liljeborgia linearis, Glaus, Die Copepoden-fauna von Nizza, p. 22, t. ii. figs. 1-8. 

 1873, Orthopsyllus linearis, Brady & Robertson, Ann. and Mag. Nat. Hist., vol. xii. p. 138. 

 1880, Gletodes linearis, Brady, Monogr. Brit. G'opep., vol. ii. p. 95, pi. Ixxx. figs. 1-14. 

 1909, Orthopsyll-us linearis, G. 0. Sars, Crust, of Norway, vol. v. p. 289, pi. cxcix. 



Female. The body, viewed from above, is narrow and elongated ; the posterior 

 margins of the segments are dentated ; rostrum blunt and slightly produced. Caudal 

 rami short ; each ramus is provided with a stout and tolerably elongated terminal bristle. 

 The specimen represented by the drawing (fig. 10) measures about 17 mm. in length. 



The antennules arc short and composed of four joints ; the second joint is armed 



(ROY. soc. EDIN. TRANS., VOL. XLVIII., 567.) 



