SCIENCE-GOSSIP. 



green preparations of the same date has dis- 

 appeared. 



The accompanying figures are designed to 

 illustrate the genus Hyalinia as met with in this 

 country, together with a few of its closer allies. 

 I may mention that I shall be glad of living 

 specimens of other species, especially those of this 

 group, and any proximate Continental forms 

 which may be figured in a subsequent paper. The 

 genus Hyalinia has the reputation of being a 

 difficult one. No one who has not tried it can 

 fully appreciate how hard it is to bring out in a 

 drawing the really important points of difference 

 between the shells of the various species. In 

 avoiding Scylla we fall into Charybdis. we 

 exaggerate the differences so that the unfortunate 

 collector finds that his shell is not eligible to be 

 this or that or anything at all. The wise and 

 learned gentlemen whose nomenclature we profess 

 to use have fallen into similar difficulties before us. 

 We find that the appropriate name lucida has been 

 applied to nearly all the species in turn. Nitens 

 has been another rock of stumbling ; and when we 

 examine plates and descriptions of foreign forms, 

 our eventual state of mind and expression of it is 

 liable to be unparliamentary. If we examine the 

 radula of the confused species light begins to 

 dawn. Variation within the limits of the species 

 is here very rare, much rarer in fact than in most 

 other mollusca. A T. nemoralis with two or three 

 teeth in each row confused is not an unusual find ; 

 but I have never noticed such a thing in the 

 Hyalinia?, unless we reckon Polita excavata, Bean., 

 as belonging to the genus Hyalinia. The actual 

 number of marginal teeth may vary a little, but 

 very little. H. cellaria, Mull., and H. alliaria, 

 Miller (figs, i and 2 respectively), have somewhat 

 similar arrangements, but there is no chance of 

 confusing the two f 1 ). The central tooth is quite 

 different ; the marginals number half as many 

 again in alliaria. These examples are interesting 

 as showing in a marked degree what I take to be 

 the more notable characteristics of the most 

 typical Hyalinia? : 



(a) The central tooth is small in comparison 



with the laterals and marginals ; 



(b) There is a very small number of laterals, 



three only in the case of these two species ; 



(c) The marginals are very long, and have only 



one point ; they are never bifid as in Conulus 



fulvus, etc. 



If we now look at fig. 3 IH. pura. Aid.) and fig. 4 



(H. nitidula, Drap.), we find a departure from this 



very definite type. The central tooth is about 



the same size as its neighbours, a condition which 



I 1 ) Since writing the above, Mr. W. Moss has most kindly 

 furnished me with a photograph of the radula of H. glabra, 

 Stud. The true glabra appears to be rare in Britain ; but I 

 propose to treat more fully of this question in a subsequent 

 paper. 



is, so far as I know, found in all other British 

 Pulmonata, except Testacella, in which it is 

 remarkably small, and the typical Hyalinia? already 

 mentioned. Pura has still the orthodox three 

 laterals only, but nitidula has four, and one transi- 

 tional tooth which resembles the marginals, 

 except for its being bicuspid to a small extent- 

 When we get to the species forming the great bulk 

 of the old genus Helix, we shall find that transi- 

 tional teeth are so frequent that it is practically 

 impossible to draw the line between marginals and 

 laterals ( 1 ). 



In figs. 3 and 4 we note again that pura has a 

 great many more marginals than alliaria or cellaria, 

 and that the otherwise more aberrant nitidula has 

 more still. They are not all shown in fig. 4 ; the 

 type remains the same throughout, but the extreme 

 ones dwindle down to a very small size. This 

 increase in numbers is accompanied by a diminu- 

 tion of size in the individual marginals, but as yet 

 each tooth is only single-pointed, and of the regular 

 form which we associate with the marginals of 

 Hyalinia. 



From Hyalinia to Agriolimax (A . laevis. Mull., fig. 5) 

 may seem a great leap, but perhaps it is not so 

 great as we should be inclined to think. Here we 

 see that the teeth are individually quite of the 

 Hyalinia type, but in respect of numbers there is 

 considerable difference. There are eleven laterals 

 and about twenty marginals, the transition being 

 much less abrupt, but yet not by any means difficult 

 to make out. On account of the large number of 

 small teeth I have only drawn a typical lateral and 

 the first and last marginal. 



There are several groups which formed part of 

 the old genus Zonites, as understood by Gwyn 

 Jeffreys and Moquin-Tandon, which for various 

 reasons have been or are being split off from our 

 Hyalinia?. We have, for example, the Polita group 

 IP. excavata, Bean., fig. 6), which pleads guilty to 

 the possession of that very improper instrument for 

 a Hyalinia, the spiculum amoris, or " love-dart " ( 2 ). 

 Polita excavata is not very much unlike nitidula in 

 respect of tongue, but it has nine laterals, instead of 

 four, and its rather numerous marginals, though 

 not bicuspid, are relatively small. The arrange- 



t 1 ) I use these terms in the sense in which they are found 

 in Mr. Taylor's Monograph (p. 152), the laterals being those 

 which are immediately at the sides of the central tooth, and 

 the marginals the remainder from the last distinct lateral to 

 the outside edge. This is also the usage of Pilsbry and 

 most modern authorities. It seems likely that the laterals 

 are homologous with the highly-developed teeth of the 

 Pectinibranchiata, and the marginals with the uncini. which 

 sometimes occur in that group. Some support is given to 

 this view by the fact that where the laterals are abruptly 

 distinguished from the marginals they are generally more 

 elaborate and fewer in number. The figures accompanying 

 the present paper will show this to be true in the case of 

 this particular group. The further inference, which I need 

 not press any more at present, is that Hyalinia is the proto- 

 type of a great part of the Pulmonata, Vitrina, Testacella 

 and Limax branching off from it In one direction, and 

 Avion, Patitla, etc., in another. 



( 2 ) It is right to add that this organ is supposed not to be 

 homologous with the spiculum of the Helicidas. 



