196 PERCY SLADEN TRUST EXPEDITION 
fauna, and that only one species of water-beetle (the Dytiscid Copelatus gardinert) was 
found in them in any numbers. This is fully borne out by the aquatic Hydrophilide : 
only two specimens (one of Phalydrus abnormalis and one of Philydrus parvulus var.) 
were found at any considerable elevation, both of them in the Mare aux Cochons plateau 
(Silhouette), over 1000 feet above sea-level. All the other aquatic Hydrophilidee 
which I collected in the Seychelles were found quite near sea-level, either in the 
coastal swamps or estuary at Anse Royale, Mahé, or in a pond near the beach in 
Félicité Island. Hydrena mahensis, though described here as a new species, is very 
closely allied to or possibly only a form of a Madagascar species: Paracymus alluaudianus 
(found in Coetivy), also described as new, is allied to a species found in Madagascar 
and in Kast Africa and Eritrea: Helochares melanophthalmus var. sechellensis is a local 
form of a very wide-spread species: Philydrus parvulus is very widely distributed in 
the warmer regions of the Old World, and occurred in Coetivy and Aldabra as well 
as in the Seychelles: Philydrus abnormalis occurs in Madagascar, British East Africa, 
Seychelles (Silhouette), Ceylon, and possibly also in Sumatra. 
Aldabra. 7 of the 9 species are aquatic and 2 terrestrial. The three species which 
occur also in the Seychelles (Philydrus parvulus, Philydrus abnormals, Dactylosternum 
imsulare) are all very wide-spread, as stated above: a fourth species Helochares melanoph- 
thalmus (represented in the Seychelles by a special form) is also very wide-spread, Of 
the 5 remaining species, the 3 species of Berosus are all known from Madagascar (one 
of them, Berosus acutispina, having very close allies in Africa and apparently also in 
Tonkin) ; Celostoma rufitarse is Madagascan and African: the Volvulus is somewhat 
doubtfully referred to an African species. The Aldabran Hydrophilid fauna therefore 
contains Madagascan and African elements, and an element consisting of species very 
widely spread in the warmer parts of the Old World. Its general nature thus appears 
similar to that of the Lamellicorn and Adephagous fauna of Aldabra (see vol. xv. of these 
Transactions, 1912, pp. 220 and 242). 
Reduction of wings. As mentioned above, the new genus Bowrdonnaisia is 
completely apterous (see p. 214). No other case of reduction of the alar organs was 
found in the Hydrophilide. [An interesting case was found in the Histeride, see 
pp. 224, 230.] 
Hydreenini. 
Hyprana, Kugelann. 
Subgenus Hyprana, s. str., Ganglbauer, Kif. Mitteleur., iv. 1, 1904, p. 197. 
1. Hydrena mahensis, sp. nov. 
Minuta, sat nitida, capite nigricante, pronoto medio infuscato marginibus sat late 
ferrugineo-testaceis, elytris fusco-testaceis, antennis palpisque pedibusque testaceis : capite 
sat dense punctato: palpis valde elongatis, articulo 2 fere zque longo ac 3 + 4, extrorsum 
arcuato, gracillimo, apice parum incrassato: prothorace transverso, ante medium parum 
angustato, angulis anticis rotundatis, pone medium fortius angustato et lateribus leviter 
