LAMB— DIPTERA : LONCH^ID^, SAPROMYZID^, EPHYDRID^, ETC. 319 



Abdomen concolorous with thorax, except that the base is often slightly reddish ; 

 dorsum with sparse scattered bristles, those on the last two segments being longer. 



Size. 2 to 2|^mm. 



Localities. Astove Island: 1907 (Thomasset). Coetivy: 24. IX. 1905. Seychelles: 

 Mahe, from seaweed on beach at Long Island, VII. 1908. 



MosiLLUs, Latreille. 



Mosillus Latreille, Hist. Nat. Ins. et Crust., xiv. (1804), p. 389. 



19. Mosillus alhipennis Loew, Stettin. Ent. Zeit., viii. (1848), p. 14. 



This species is recorded from S. Europe, Egypt and Teneriffe. The Cambridge 

 Collection contains several specimens from Durban, Natal. 



Locality. Seychelles. Mahe: one specimen from Anonyme Island, I. 1909. 



Enchastes, n. g. (PL 15, fig. 21). 



A single specimen (in excellent condition) of a new genus near Mosillus was in the 

 collection ; though but a single specimen is available it is thought best to give a full 

 description of the proposed genus, as the insect is of considerable interest. The genus 

 Mosillus was long considered to be in the Chloropidse, but was finally placed among the 

 Ephydridae from the presence of certain structural details, although the general facies is 

 very strongly that of a black Chloropid. The present insect is similar to Mosillus in 

 many important respects but is more Ephydrid in form and is of a dull green surface 

 which is slightly shagreened, recalling the texture of Pelina. 



Head. Eyes bare, long, oval with axis vertical ; jowls deep. Antennae with 

 rounded third joint, which is but little larger than the second ; the basal bristle on 

 the second joint is minute though evident. The top fronto-orbital bristles are small and 

 in line with the front ocellus, the other fronto-orbitals are reduced to hairs. Small inner 

 verticals and a pair on the frons just beyond the front ocellus. The most striking 

 difference between Mosillus and Enchastes is best seen on a front view (PI. 15, fig. 22). 

 In Mosillus the sutures extending from the ends of the lunule each side and separating 

 the face from the cheeks are very nearly parallel ; the eyes are round ; hence the cheeks 

 widen greatly from the antennal level downwards. In the present genus these sutures 

 diverge somewhat ; the eyes are long-oval and hence the cheeks are much more nearly 

 of constant breadth from the antennal level downwards. 



The face is protuberant and has a large oblong shining knob : the four facial bristles 

 stand on extremely minute hillocks. The prelabrum is very pi'otuberant and is rect- 

 angular or spade-like in profile. 



Thorax and scutellum, dorsum with the surface minutely granulate and covered 

 with short bristly hairs instead of the fine hairs of Mosillus. The last pair of dorso- 

 central bristles, a single notopleiu-al bristle just before the wing base, two mesopleural 

 which are not very strong, two scutellars crossed at the tip. The scutellum is roinided 

 at the tip. Wings and legs mucli as in Mosillus. 



Type, the following species. 

 SECOND SERIES— ZOOLOGY, VOL. XV. 41 



