130 DR. C. CHILTON ON THE 



Genus 3. Act^cia, Dana, 1853. 



AcUpcia, Dana, U. S. Explor. Exped., Crust, ii. p. 7134 (185.3). 



Actmcta, G. M. Thomson, Trans. N. Z. Inst. xi. p. 249 (1879). 



Cylloma, Budde-Lund, Isopoda Terrestria, p. j6 (188;j). 



Actmcia, G. M. Thomson, Proc. Roj'. Soc. Tasmania, 1892, ji. 12 (st'j)arate copy). 



Generic description. — Body convex, capable of rolling into a ball, surface spiny. 

 Metasomc not abruptly contracted, terminal segment very short. Elagellum of anteanf« 

 4-jointed. Eyes very large and promiDcnt, on oval elevations along the sides of the 

 head. Maxillipedes with the terminal portion large, lamellar. Legs rather short, not 

 increasing much in length posteriorly. None of the opercular plates of the pleopoda 

 with air-cavities. Uropoda short, not projecting much beyond the outline of the body ; 

 base broad and flattened, outer portion produced, outer ramus short, inserted at the end 

 of the base near the inner margin ; inner ramus slender. 



Remarks. — I propose to retain the genus Actcecla, Dana, for the following species, and 

 give for it the ahove diagnosis. In many respects it appears to resembie Arnuul'dloimcus, 

 Ulianin, with which Budde-Lund thought it to be identical, but that genus differs 

 considerably in the form of the head and in possession of air-cavities in the first two 

 pleopoda, and as it presumably belongs to the Oniscidce, it probably differs also in the 

 terminal portion of the maxillipedes, but on this point I can get no definite information. 



Cijlloina, Budde-Lund, agrees so well with the genus in question in the eyes, and 

 terminal uropoda and general shape, that T think it must be the same, though Budde- 

 Lund describes it as having air-cavities in all the opercular plates of the pleopoda ; this, 

 however, perhaps arises from the fact that he had only a single badly-preserved 

 (probably dried) specimen, and natui-ally thought that it belonged to the ArmadilUdce 

 and came near to Armadillo. 



Hayer's genus Actoiiiscus is, as he points out, nearly related to Actcecia, and tlie 

 difference that he gives in the antennae is more apparent than real, for Actcecia has only 

 four distinct joints in the iiagellum, and some of the other differences are of subsidiary 

 importance. On the other hand, the cephalon in his species is more Hke that of Arma- 

 dilloniscus, but whether it also resembles that genus in the possession of air-cavities in 

 the first two pleopoda or not, I cannot say. In general ajspearance it certainly appears 

 to resemble Acta'cia much in the same way as Sci/phacella resembles Scyphax. 



The two New Zealand species of Actcecia may be distinguished thus : — 



Eggs large, crescentic, outer branch of uropoda large, dilated distally A. euchroa. 



Eyes moderate, outer branch of uropoda minute, acute at apex A. opitrensis. 



1. AcTiECiA EUCHROA, Dana. (Plate 15. fig. 3.) 



Actcecia euchroa, Dana, U. S. Exploring Exped., Crust, ii. p. 734, Plate 48, fig. 6 (1853). 



Actcecia euchroa, Miers, Cat. N. Z. Crust, p. 101 (1876). 



Actcecia euchroa, G. M. Thomson, Trans. N. Z. Inst xi. p. 249 (1879). 



Armadilloniscus euchroa, Budde-Lund, Isopoda Terrestria, p. 239 (1885). 



Actcecia euchroa, Filhol, Mission de Pile Campbell, p. 443 (1885). 



Actcecia euchroa, Thomson & Chilton, Trans. N. Z. Inst, xviii. p. 158 (1886). 



Actcecia euchroa, G. M. Thomson, Proc. Roy. Soc. Tasmania, 1892, p. 12, Plate ii. figs. 1-8 (1892). 



