ON NEW BRITISH ENTOMOSTUACA. 231 



18. On Two British Entomostraca belonging- to tlic Orders 

 Copepoda and Ostracoda. By 0. Stewakdson Brady, 

 M.D., LL.D., D.Sc, F.R.S., C.M.Z.S. 



[Received December 20, 1912 : Read February 18, 1913.] 

 (Plates XXXVIII.-XL *) 



Index. Page 



Diaptomus pusiUus, S]}. n 231 



Amnella subsalsa, gen. et sp.n 232 



The two species here described are the result of a recent i-e- 

 examination of material collected many years ago. The first 

 named species occurred abundantly in a gathering made by the 

 Rev. CanOn Xorman, F.R.S., in Loch Ness, Scotland. The other 

 species is, unfortunately, represented by only one specimen taken 

 by myself near Arundel in Sussex. 



Order Copepoda. 



DiAPTOMUS PUSILLUS, sp. n. (PI. XXXVIII.) 



Female. — Length 1 mm. Body slender ; seen dorsallythe anterior 

 portion (cephalothorax) is quite thrice as long as broad, its anterior 

 extremity well rounded, posterior broadly truncate with acutely 

 mucronate lateral angles (fig. 3). Abdomen two-segmented (fig. 3), 

 the first (genital) segment twice as long as the following segment, 

 wide and bulbously dilated at the base, which is produced laterally 

 and bears two aculeiform setfe ; caudal rami not much longer 

 than broad, terminal setse very feebly plumose. Anterior anteniije 

 slender and almost entirely destitute of marginal hairs, extending 

 when reflexed as far as the apices of the caudal setse (fig. 1). 

 Basal joint of the last pair of legs (fig. 4) somewhat dilated, its 

 outer margin prominent in the middle and bearing a short spine- 

 like seta ; inner branch short, simple, inai-ticulate, truncated at 

 the apex, which bears two or three very minute setse ; outer branch 

 about three times as long as the inner branch, its last joint forming 

 a strong dagger-shaped claw to the dilated base of which is 

 attached a short spine. Ovisacs very small, spherical, containing 

 not more than one or two ova. 



Male somewhat smaller than the female, length 0-98 mm. 

 Right anterior antenna slender, very slightly dilated in the 

 middle (fig. 2), the 13th joint bearing a single strong spine, the 

 10th and 11th each a very small needle-like hair, the other joints 

 almost or entirely hairless ; antepenultimate and penultimate 

 joints simple, elongated, last joint small, bearing a few apical 

 filaments (fig. 6). Last pair of legs strongly developed (fig. 5), 

 the right much the larger and reaching beyond the extremities 



* For explanation of the Plates see pp. 233-4. 



