MARINE CRUSTACEANS. 441 



Genus Conchoderma Olfers, 1814. 



4. Conchoderma hunteri Darw., 1851. Darwin, i. p. 153. 



Hoek (" Challenger" Cirripedes) regards this form as a variety of G. virgata (Spengler), 

 1790, but the latter has not been found on sea-snakes, while C. hunteri appears to have 

 that habitat, Darwin's specimen and the present both so occurring. The only others 

 recorded (Stebbing, Willey's Zool. Results, vol. v. p. 676) made the pardonable mistake of 

 attaching themselves to submarine cables. This fact lends support to the presumption that 

 the species are distinct. 



Genus Lithotrya Sowerby, 1822. 



5. Lithotrya dorsalis (Ellis), 1786. Darwin, i. p. 351. 



I am unable to regard the Maldive specimens of this genus otherwise than as belonging 

 to varieties of this West Indian species. Two forms may be recognised, the type (var. A) 

 not being present. 



B. Var. maldivensis n. 



Differs from the type in the following points : (1) There is a very faint ridge within 

 the carina. (2) The caudal appendages are rather less than half as long again as the last 

 pedicel. (3) There is a shallow notch on the maxilla of the right side, though none on 

 the left. (4) The tergal edge of the scutum is slightly concave. (5) The scuta are longer 

 than in L. dorsalis. (6) The carina is shorter. 



These latter two features, however, may well be due to a difiference in the manner in 

 which the specimens have become worn by the sea. 



C. Var. rugata n. 



Differs from the preceding variety in the following points: (1) The carina has a fairly 

 strong ridge. (2) The caudal appendages are only very slightly longer than the pedicel of 

 the last limb. (3) The rostrum is bordered by 6 scales instead of 3. 



This species lives on the under side of overhanging coral rocks and is always so placed 

 that its capitulum is at the opening of the hole. I am at a loss to understand how some 

 of Darwin's specimens came to be reversed. For some remarks on its importance in the 

 disintegration of coral rock, see Mr Gardiner's Paper in Part III. of this publication (p. 337). 



Family Balanidae. Genus Balanus Da Costa, 1778. 



6. Balanus tintinnahidum (Linn.), 1758. Darwin, ii. p. 194. 



The specimens, which were taken in various localities, are all small and belong to the 

 var. communis. 



7. Balanus amphitrite Darw., 1854. Darwin, II. p. 240. 



The specimens are coloured pink and much resemble B. tintinnabulum. They are small 

 and have given me much trouble, but I have finally placed them here on account of the 

 undoubted absence of pores from the radii, and because the mandibles agree best with 

 Darwin's description for this species. They were taken in Fadifolu Atoll. 



