SCIENCE-GOSS//\ 



n 



ARMAir 



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III 



KOll) 



i..\\i)Siii;i.i,s 



AND \KVV Sl'IX'IKS Dl' I'l.lXTOI'NI.IS. 

 Hy G. K. (ii'UK, K.Z.S. 



(Cunttniiird /rout fiat^e 17.) 



J'.'d/o/iylis (Syiesia) calii^iiiasn (figs, looac) from 

 Aniljagamiiwa, Ceylon, was descributl and figured liy 

 Mr. Sykcs, in the " I'roceedings of the Malacological 

 Society of London," iii. (1S9S), p. 72, t. 5, ff. 21, 22. 

 The shell is lenticular, narrowly unil)ilicated, ochrcoiis 

 corneous, opa(|ue, very finely and regularly ribbed, 

 the ribs being rather more prominent above than 

 below ; it is acutely keeled at the periphery, with a 

 raised spiral line above the keel, quite clo.se to it, as 

 far as the apical whorl. The spire is conical, the ape.\ 

 obtuse, the suture impressed. There are five very 

 slowly increasing whorls, flattened above, tumid 

 below, the last scarcely wider than the penultimate, 

 not descending in front. The aperture is almost 

 vertical, lunate, and the peristome simple, acute. The 

 parietal armature consists of two simple, sub-vertical 

 plates H hich are somewhat thickened and truncate at 

 the lower, and attenuated at the upper extremities ; 

 these plates are separated by a distance of a quarter 

 of a whorl, ami the posterior one is the stronger (see 



100. — PlectoPytis citliginosa. 



fig. \ood, which shows the parietal wall with its two 

 plates). The palatal armature is in two vertical 

 series : the anterior series consists of an obliquely as- 

 cending short (|ua(lrate tooth near the periphery, and 

 below this an obliquely descending lamelliform tooth, 

 with a slight, horizontally elong,Ued denticle below 

 its posterior extremity ; the posterior series is similar 

 to the anterior one, but the teeth are stronger and 

 thicker in the former, while there is in addition a 

 horizontally elongated denticle on the anterior side of 

 the upper tooth. The specimen shown in figs. 

 loo<7-<- measures 6 millimetres in diameter, alt. 3 

 millimetres, and is in the collection of Mr. I'onsonby. 

 The armatures are fijured from the type specimen in 

 the collection of Mr. Sykes, who kindly permitted me 

 to open the shell for the examination of the armature. 

 PUdopylis (Sykcsia) clalhralitla, var. compressa, 

 (figs. ioi<i-c) was described and figured by Mr. 

 Sykes in the " Proceedings of the Malacological 

 Society," iii. (1S9S), p. 72, t., 5, ff. 13, 14. It 



differs from the type in being more elevated, in the 

 more convex spire and the narrower umbilicus, while 

 the raised ribs are scarcely visible. The armature is 



Fi(j. lot. — I^icctopytis cial/ii-atnla var conipressa. 



similar to that of the type. The specimen figured is 

 in Mr. Ponsonby's collection ; it measures 5 milli- 

 metres in diameter, altitude 2'5 millimetres. 



Plcdopylis fraiii:oisi (figs. \02a-c\ from Dco-ma- 

 Phuc, Tonkin, was described and figured by Dr. H. 

 Fischer, in the "Journal de Conchyliologie, xlvi. 

 (1898), pp. 214-218, ff. I, 3, 4 (part published March, 

 1899). The shell is dextral, deeply and widely um- 

 bilicaled, corneous, striated, and decussated with 

 microscopic spiral lines above, which become obsolete 

 at the periphery, the lower surface smooth and a 

 little shining. The spire is depressed, conical, the 

 apex prominent and the suture distinctly impressed. 

 There are ^\ whorls, which increase slowly and regu- 

 larly, and are somewhat flattened above and tumid 

 below. The last whorl is at first obsoletely keeled 

 above the periphery and angulated .at the umbilical 

 region near the parietal callus ; it descends shortly 

 and suddenly in front. The aperture is a little 

 oblit]ue, subcircular ; the peristome white, a little 

 thickened and reflcxed, its margins united by a 

 parietal callus. The parietal armature is composed of 

 two strong, obliquely divergent, transverse plates, the 

 anterior one shorter, rounded at the upper and giving 

 oft" an anterior ridge at the lower extremity ; a short 

 thin horizontal fold occurs immediately above it ; the 

 posterior plate longer, truncate at the upper, attenuated 

 at the lower extremity. A free thin horizontal fold 

 occurs below these plates, terminating on the one side 

 just below the anterior plate, and on the other just 

 in front of the posterior plate. (See fig. I02(/, which 

 shows part of the parietal wall with its armature). 

 The palatal armature consists of six folds ; the first, 

 rather short, thin, horizontal, near the suture ; the 

 second longest of all, horizontal, deflected at the 

 posterior extremity and becoming slowly attenuated 

 anteriorly ; the third, fourth, and fifth stronger, semi- 

 circular, oblique, their anterior extremities a little 

 reflcxed, their posterior ones a little deflexed ; the 

 sixth thin, long, horizontal ; the second, third, fourth, 

 and fifth give off, about the middle, from the lower 

 side, a slight callous ridge w hich connects them inter 

 se ; between the posterior extremities of the fifth and 



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