46 BEITISH FRESHWATER EHIZOPOBA. 



of the test (fig. 129 cl). In length they vary greatly but 

 are usaally of about the same length on the same test. 



Although in a few localities, such as the moors of 

 the North Riding of Yorkshire and the swamps of 

 New Jersey, U.S.A., living individuals are fairly 

 numerous, none were observed in process of division 

 or conjugation. 



In the United States a variety is found in which 

 the spines are acicular and scattered over the whole 

 surface of the test. 



Fig. 130. — Test of Placocista spinosa, witli abnormally distended aperture. 

 X 270. From Llyn Llydaw, Snowdon. (Cr. S. West.) 



The aperture is sometimes found widely distended 

 (fig. 130 ft), in side view showing as a notch with 

 convex sides (fig. 130 5), but this probably only occurs 

 permanently in empty tests, the living animal usually 

 keeping it closed. 



2. Placocista jurassica Penard. 

 (Plate XL, figs. 7-9 ; and PI. XLII, fig. 1.) 



Placocysia jurassica 



Pbnakd in Rev. Suisse Zool. XIII (1905), pp. 611-612, pi. xiv, fE. 29, 



30; op. cit. XIV (1906), p. 136; Sai-codines in Oat. Invert. Suisse 



(1905), pp. 105-106 ; in Brit. Antarct. Exped. I (1911), pp. 220, 250. 

 Evans in Proc. R. Phys. Soo. Edinb. XVII (1907), p. 11, table 1. 

 Heinis in Arch. Hydrobiol. V (1910), p. 109. 

 Brown in Jrn. Linn. Soc, Zool. XXXII (1911), p. 83, pi. ix, ff. 16- 



18 ; in Ann. Scott. Nat. Hist. 1911, p. 229 ; in Scott. Natui-. 1912, 



pp. 109, 112. 

 Wailes in Naturalist, 1913, p. 148. 

 Placocista jurassica 



ScHOTJTEDEN in Ann. Biol, lacustre, I (1906), pp. 368, 369. 



