SCIENCE-GOSSIP. 



285 



periphery, and the fimbriae are coarser, longer and 

 more persistent. The specimen shown in figs. 72 

 a and I, from Sse-Tchuan, China, is one of two 

 sent to me by Dr. von. Mollendorff ; it measures : 

 major diameter, 75 millimetres ; minor diameter 

 65 millimetres : altitude, 375 millimetres. 



fytis trochospira (figs, y^a-e), from Mount 

 Licos, Cebu, Philippine Islands, was described by 

 Dr. von Mollendorff in the " Jahrbuch der Deuts- 

 chen Malakazoologischen Gesellschaft," xiv. (iSS7), 

 p. 273, and the shell was figured in the same work, 

 t. S, f. 9. The armature, however, was not illus- 

 trated, and I believe the figures now given are the 

 first which have appeared. The shell is dextral, 

 widely and deeply umbilicated, depressed-conical, 

 light corneous, finely ribbed above and striated 

 below. The spire is conical and the suture im- 

 pressed. There are six narrow rounded whorls, 

 which increase slowly and regularly ; the last, 

 considerably wider than the penultimate, has a 

 thread-like keel at the periphery, is angulated 

 round the umbilicus and does not descend in front. 

 The aperture is diagonal, lunate ; the peristome 

 white, a little thickened and reflexed, the margins 

 being slightly convergent and united by a scarcely 

 raised sinuous ridge at the parietal callus. The 

 parietal armature consists of two long, parallel, hori- 

 zontal folds, which revolve over nearly half a whorl, 

 the upper one being the stronger and united to the 

 ridge at the aperture, while the lower one is thinner 



d 1 



—Pltctopylil trochospira. 



and terminates at a short distance from the ridge ; 



horizontal fold occurs posteriorly 



a little below the upper fold (see fig. 73;, which 



the parietal wall of the shell with its 

 The palatal armature is composed of five short, 

 thin, horizontal folds, which descend a little 

 anteriorly ( -cc fig. jjd. which shows both the 

 parietal and the palatal armatures from the 

 posterior side). The specimen figured is in the col- 



of irofessorOscar Boettger, of Frankfort, by 

 whom this shell -which measures : major diameter, 

 4 millimetres; minor diameter, 35 millin 

 altitude, 2 millimetres was obligingly lent ti 



■ 



larger and mur li lighlei in 



: . there are alvi certain difference! in the 



PlectopyUs trochospira, va.r.bolioknsis( i ). Two speci- 

 mens kindly lent to me by Mr. Ponsonby, labelled 

 with the manuscript name, " Plectopyln trochospira 



Fig. 74. — Ptcctopylis trochospira var. bohotensis. 



var. boliolensis (Mollendorff)," certainly represent a 

 distinct variety. They are smaller than the type, and 

 the umbilicus is narrower. The armature is nearly 

 identical, but the palatal folds are connected at 

 their posterior terminations by a very slight trans- 

 verse sinuous ridge, plainly discernible externally 

 through the shell-wall. 



(To be continued.) 



MINERAL PHOSPHORESCENCE 



AND X-RAYS. 

 TN the early 'part of last year, Mr. John E. 

 Burbank, of the Jefferson Physical Laboratory, 

 Harvard University, was experimenting en fluor- 

 escent screens for the X-rays. His attention was 

 directed to the fluorescence of minerals under the 

 action of these rays. He followed up the subject 

 with some notable results, which, though probably 

 not entirely new, are interesting 



Fluorite, when exposed to X-rays, phosphoresces 

 with a bluish-white light, which continues for a 

 long time after being removed from the influence 

 of the rays. 



About two-thirds of the minerals tried were 

 found to be phosphorescent to a greater or less 

 degree, the group containing calcium is most 

 susceptible to the action of these rays. Of sixteen 

 specimens tried, twelve of this group were phos- 

 phorescent, with light varying from pure white to 

 yellowish red. The felspar group is also acted 

 on by the rays, as are some others of the silicates ; 

 but the general ore-bearing minerals are non- 

 phosphorescent. 



It is well known that heat and light radiations 



produce luminous effects in the case of mineral 



crystals. Apparently these effects are very much 



like those set in motion by the X-rays ; but if the 



crystals are heated and then exposed to the radia- 



froin X rays the character of the light 



i. often changed. In his description of these 



intents, Mr. Burbank mentions that iliis is 



e with glass, fluorite and calcite. in a few 



ra.'-, the light is intensified alter the mineral 

 1 rystala have been heat' d. 



(i, Plutopylti trochotpira vai boholtn r, n. var. (flo, ;ii, 



.!,!!. t lr '.in 1 1.' I > J.' Ill l>< III: 'nulls I .in- 1 ti,ivlli|; .1 n.H rOVt I I 



iimbllli tti 13 mill tn ml llamatar. 



I iniiinN'ii' altitude, 173 millmelrei Habitat, Bolioi 

 Philippine I I.iimI . Type In Mi. I' .nnliy'. i i,l 



1. cllon, 



'• 3 



