SCIENCE-GOSSIP. 



17 



has (ibligingly searched ihe Brilish .Museimi collcclicm 

 for these types, but without success. The species 

 appears to be rare, for since it was first de- 

 scribed, it has remained unoljserved until Mr. H. 

 B. Preston found a single specimen at Patapolla, 

 Ceylon, as recorded by Mr. E. R. Sykes 

 ("Proc. Malac. Soc, London," iii., 189S, p. 66), 

 and Mr. O. Collelt subsequently found two 



Fiif. 99. — Plcclopylis l<iciUata. 

 specimens at Haputale (Sykes, op. cit. p. i5o). 

 The three specimens referred to agree with the 

 figures in "Conchologia Indica," and it may, therefore, 

 be safely assumed that they are correctly identified, 

 and to Mr. Sykes belongs the credit of first pointing 

 out the true systematic position of the species. The 

 shell is convexly conical, narrowly umbilicated, 

 dark corneous, translucent, finely and regularly 

 ribbed, with a double keel at the periphery and a 



third a little above it, the lowest and uppermost 

 b'iing provided with a fringe of coarse, curved, 

 deciduous hairs. There are six convex whorls, which 

 increase slowly and regularly, the base a' little 

 shining, tumid around the narrow umbilicus and 

 concave towards the periphery. The aperture is sub- 

 quadrate, elongated, the peristome simple, acute. 

 The parietal armature consists of two simple oblii^uely 

 ascending folds, separated by a distance of half a 

 whorl, having the upper extremities somewhat 

 attenuated and the lower truncate. (See fig. 990?, 

 which shows the parietal wall with its two folds). The 

 palatal armature is composed of : first, a short, hori- 

 zontal fold below the periphery, a little farther back 

 but in a line with it a strong lamelliform denticle, 

 ascending obliquely ; secondly, three denticles in a 

 line horizontally and about equidistant, the posteiior 

 one strongest ; thirdly, a short slight horizontal fold 

 near the lower suture, rising near the aperture and re- 

 volving as far as the second denticle. (See fig. 99e, 

 which shows the inside of the outer wall with the 

 palatal armature). The specimen shown in figs gga-f 

 measures 6 millimetres in diameter, altitude 3 '5 milli- 

 metres; it is one of the shells collected by Mr. Collett 

 and is in Mr. Fonsonby's collection ; the armatures are 

 figured from the specimen collected by Mr. Preston 

 which is in Mr. Sykes' collection. 



{To be conthiucii.) 



BRITISH FRESHWATER MITES. 

 By Charles D. Soak, F.R.M.S. 



GENUS LIMNESIA KOCH. 



{Contimu'd frotii ]'ol. I',, //i^'V 361.) 



'T^IIE next genus that has yielded the largest number 

 ■'• of species in this country is Z2«««j/fl. In this we 

 have six species. Three are very common, but not so 

 the others. There are a great many species known 

 and described from different parts of the world ; there- 

 fore I do not see any reason why more should not be 

 recorded as British. 



The mites belonging to this genus are characterised 

 as having the body soft-skinned, legs well supplied 

 with swimming hairs, and the fourth pair of feet with- 

 out claws. There are six discs on the genital plates ; 

 three on each side. The mandibles are in two por- 

 tions ; eyes wide apart. 



I. — Liinnesia histrionica Hermann, 1S04. 



Female. — Body : Oval in form. Length about 

 1 75 mm. Width about i -40 mm. Colour a bright 

 scarlet, with very dark brown markings. 



Legs. — First pair about i'40 mm. Each pair 

 gradually gets longer ; the fourth pair being about 

 2 '20 nnn. They are all well supplied with swimming 

 hairs. The first three pairs of feet have claws, the 

 fourth pair have not ; but the tarsi are extended 

 almost to a point, near which apex is a strong spur or 



bristle as seen in fig. i. The fourth pairs of legs of 

 all members of this genus are modified in the same 

 manner ; this applies to males as well as females. 

 This is one of the important points of identification in 

 this genus, but it is not confined to it only, as we 

 shall later see. Colour, blue, sometimes very bright ; 

 at others of a slaty tint. 



Ei'iMERA. — (Fig. 2.) Arranged in four pairs, two 

 on each side of the median line. In colour they are 

 the same as the legs, and all other chitinous parts. 



Palpi. — Large and long, about 0^92 mm. in length. 

 On each second segment is a small peg (fig. 3). 



Genital Area. — This is composed of two plates. 

 On each plate are three discs, this is no doubt the 

 correct arrangement, but as usual, they vary in num- 

 ber. I am continually finding specimens with two on 

 one plate, three on another, four on one, five on 

 another ; and so on. Such irregularity can only be 

 sports. Koenike, in his work on Hydrachnidae of 

 Madagascar, 1898, describes and figures a male and 

 female Liinnesia aspcra with four discs on each plate. 

 I believe this is the only known species that possesses 

 this remarkable distinction. 



