GASTROPODA LAMBLLIB RAN CHI A . 
199 
Helicina intus-pUcata, Pfr. (1850) = smithiana^ Pfr. (1866), and H. 
cumingiana (Pfr.), both from Hayti ; Bland, Ann. Lyc. N. York, xi. 
pp. 149 & 150. 
Helicina scrupulum (Bens.), Andaman Islands ; Hanley & Theobald, 
Conch. Ind. p. 53, pi. cxxx. figs. 8 & 9. 
Helicina anozona^ Martens, P. Z. S. 1875 [April, 1876], p. 649, Coban, 
Guatemala ; H. martensi, near citrina (Grat.), Issel, Ann. Mus. Genov, 
vi. [1874] p. 444, pi. vi. figs. 23-25, Labuan : spp. nn. 
Troschel states that the radula of Hydroccena and Georissa (Blanf., 
1869) agree considerably, but he is disposed to keep them as distinct but 
hearly allied genera, because Georissa is terrestrial \Hydroc(x.na^ however, 
does not live in water, but only in damp spots] ; he thinks that Acmella 
tersa (Blanf.) is near Eydrohia, the number of five plates in each 
transverse row being probably an error ; Realia (Gray) belongs evidently 
to the CyclostomatidcB, its radula most resembling that of Cistula. Gebiss 
d. Schnecken, ii. pp. 163 & 164.' 
Hydroccena pyxis (Bens.), illex (Bens.), frustillum (Bens.), rawesiana 
(Bens.), all from Burma, and sarrita (Bens.), Garo Hills ; Hanley & 
Theobald, Conch. Ind. p. 48, pi. cxvii. figs. 3-7. 
SOLENOOONOH^. 
\_Cadulus'] Helonyx Jeffrey si ^ new name for Cadulus suhfusiformis of 
Jeffreys, Brit. Conch., which is distinct from suhfusiformis (Sars), both 
being found in the Mediterranean. Monterosato, Atti Acc. Palerm, 
1875, p. 20. 
LAMBLLIBKANOHIA. 
The structure of the gills of the Bivalves has been studied by 
C. Posner in Anodonta and some marine genera. According to him, the 
gills are plates of conjunctive tissue, which contain blood in lacunar 
intervals, and are provided with an internal skeleton of parallel straight 
solid rods, probably of chitinous nature, and with numerous channels 
taking up water from without; the afferent and efferent vessels or 
arteries and veins are not sharply separated one from the other, but the 
main movement goes in some parts towards the heart and in others in 
the opposite direction. Williams is wrong in attributing merely respi- 
ratory functions to those vessels which are supported by the chitinous 
rods, and in denying lateral communications and ramifications in them. 
The most simple form of the gill is exhibited by Anodonta and Unio, a thick 
continuous plate with very copious conjunctive tissue ; that of Bcrohi- 
cularia comes near it ; but in Pholas, Venus^ My a, Ostrea, Solen^ Soleno- 
curtus, and Pinna, the plate gradually becomes longitudinally plaited, 
ridges arising on both surfaces ; in Pecten and Mytilus these ridges are 
entirely separated by discontinuity instead of mere depressions, and 
become thread-like, the threads answering in Pecten to the primary, and 
in Mytilus to the secondary, system of ridges in the continuous gill. 
Arch. mikr. Anat. xi* pp. 517-560, pis. xxxi. & xxxii. 
