1919.] E. W. Vredenburg : Shells of the family Doliidœ. 149 



fig. 3). 1 The radula of Pirula, judging from that of Pirula reticulata (Troschel, op. 

 cit., pi. xx, fig. 12), is essentially of the same type as that of Dolium perdix. 

 Further observations on the radula of various species of Dolium would be of great 

 interest. 



In a general way, Eudolium seems to be somewhat of a synthetic group in 

 which are united some of the characters of Dolium, s. str. , of Malea, of Pirula and 

 of the Cassididse. Nevertheless its relationship to Dolium, s. str. is of the closest 

 character and entitles it to rank perhaps only as a section rather than a subgenus. 

 It may here be mentioned that Dolium cinguliferum (Bronn) [= Dolium fasciatum 

 (Borson) non Bruguière ] of all species the one nearest related to the genotype 

 D. crosseanum has been referred to Dolium, s. str. by Cossmann, who nevertheless 

 gives a figure (Essais Paléocouch., V, pi. vi, fig. 10) in which there is no indication 

 of an umbilicus, while, on the contrary, Sacco has figured a specimen regarded as a 

 variety also of Dolium cinguliferum (Moll. terr. terz. Piem. e Lig., 1904, part XXX, 

 pi. xxii, fig. 5) which shows distinct traces of the tubercles that characterise other 

 forms of Eudolium. The sequel of these observations deals with the case of Dolium 

 tessellation which, until an advanced stage of growth, exhibits the essential characters 

 of Eudolium, but finally, when fully adult, becomes similar to Dolium, s. str., and I 

 have suggested that this may afford some guide as to the derivation of the one group 

 from the other, as is further indicated by their geological history. If we adopt the 

 grouping here proposed, Dolium, s. str. is not known from any strata older than 

 upper miocène, the only recorded fossil occurrences being in eastern countries, India 

 and Java, while the group, at the present day, is mostly eastern. Eudolium already 

 occurs abundantly in the oligocène, having been discovered, so far, in a fossil condi- 

 tion, only in Europe. Pirula is much more ancient and goes back to the cretaceous. 



II. — The specific distinctness of Dolium maculatum (Lam.) Desha yes 

 and Dolium (Eudolium) tessellatum, Bruguière. 



INTRODUCTION. 



Amongst the beautiful illustrations to Reeve's monograph of the genus Dolium 

 attention may particularly be drawn to four, of which the two first are referred to 

 Dolium fimbriatum, Sowerby (species 3), the next one to Dolium maculatum, Lamarck 

 (species 4), and another to Dolium costatum, Deshayes (species 8). 



In his Manual (Vol. VII, page 264) Tryon rather emphatically asserts the 

 specific identity of these three forms with which he further unites as synonyms a 

 certain number of forms described as distinct by various authors. Tryon neverthe- 

 less maintains the three forms costatum, maculatum and fimbriatum as three separate 

 varieties or races of a species costatum. No further discussion of Tryon' s conclusions 



l Troschel (op. cil , Vol. I, p. 227) has briefly described, without figuring them, the radulse of two shells which he 

 has referred to " Dolium maculatum, Lam. (= iesselatum, Encycl.) and D. costatum, Desh.," both of which seem to 

 resemble closely that of Dolium perdix. The exact identity of the two shells in question is unfortunately, for the present, 

 uncertain. 



