WEBB : BRITISH SPECIES OF TESTACELLA. 55 



critical, perhaps it would be useful in the light of the point 

 brought out and touched upon, to examine the critic's description 

 in detail. 



Mr. Collinge describes the anterior portion of the penis as 

 being '■ sometimes dilated in a somewhat caecal-like form," and 

 one acquainted with the anatomy of T. haliotidea might fancy that 

 Mr. Collinge had seen the structure alluded to above, and that 

 the dilatation refers to an apparently lateral outgrowth of the 

 penis, which is, of course, a small caecum. A reference on the 

 other hand, to the figure supplementing his description (repro- 

 duced, reversed in figure 8), shows that Mr. Collinge is not 

 familiar Avith the characteristic "tongue-like caecal process" 

 mentioned by Mr. Ta}lor, and found to be constant in British 

 examples by the present writer, or at least, has not grasped its 

 true configuration. The figure presents two swellings, one on 

 each side of the penis, and as this organ is not shaded, it is 

 further left to the imagination whether there may not be, after 

 all, but one swelling extending all round the structure. 



Mr. Taylor's sketch (reproduced in figure 5) at first sight, 

 and taken by itself, is not very much more definite, though it will 

 be seen that in reality it is more accurate. Both of the authors 

 quoted from, allude to the caecum as occurring on the lower 

 (anterior) part of the penis, whereas it will be seen from Plate VI. 

 figure la that what they consider to be the upper portion of 

 that organ is but a combination, apparently, of the flagellum 

 and vas deferens which run side by side for some dis- 

 tance before they join the true evaginable penis, which shows 

 by transmitted light a very different structure from them, as the 

 bases of papillae, with which the penis is seen to be covered 

 when extruded, are visible through its walls. 



Further, in the specimens from seventeen different localities, 

 the spermatheca is not round, but of a slightly pear-shaped oval, 

 indicated by Mr. Taylor. 



With regard to foreign examples, the writer's personal knowledge is at 

 present confined to " Testacella dubia Poll." — received from Turin through the 

 kindness of the describer, Signor Pollonera — which agrees with British examples 

 of T. haliotidea in the shape of the penis, and is put down as a form of this 

 species in the Check-list. A resume of work other than that of Lacaze- 

 Duthiers bearing upon the point at issue, in Continental specimens of 

 T. haliotidea, is given below : — 



1855. Moquin-Tandon. — " Histoire naturelle des Mollusques terrestres 

 et fluviatiles de France," Plate V., fig. 16. 



