174 IJKLOGONA. 



x ger like " dart," and a gland or glands inserted upon or above this 

 sack, the so-called "digitate glands" or mucus gland. 



The presence of these organs was early noticed by European mal- 

 acologists, but their significance has been only recently recognized. 

 Semper in 1874 made two divisions of rib-jawed Helices, those 

 genera with no accessory organs on genitalia, and those with such 

 accessories; and in 1888 the writer used these features of the 

 gehitiitia as diagnostic of various groups of Helices, elaborating the 

 idea in a later paper (1892). Meantime Dr. H. von Ihering issued 

 -a paper of great merit, " Morphologie und Systematik des Genital- 

 apparates von Helix," in which he proposes to restrict the family 

 Helicidce to snails with grooved or ribbed jaws and possessing 

 the* dart apparatus, including therein as genera Xerophila, 

 Fruticicola, Helix ( Pentatsenia), Campy Icea, Gonostomu, Ihrcasia 

 (=^Eulota), and Cochlostyla. In the following pages I have adopted 

 all of these groups as genera (although altering the names of most 

 of them), and with the exception of Campylcea and Dorcasia, they 

 are retained with the limits defined by von Ihering. I need give 

 no other expression of the high esteem in which I hold v. Ihering's 

 work, than this use of it. -It should be added, however, than many 

 genera not noticed in von Ihering's paper, are now included in this 

 group, some of which have ribbed, some smooth jaws. His family 

 diagnosis of " Helicidse ", therefore, does not cover nearly all the 

 forms here grouped under Belogona. 



The relationship of the Belogona to the Epiphallogona is dis- 

 cussed in the introductory portion of this volume. It remains to 

 study the internal affinities of its numerous genera. It has been 

 seen that the Belogona differ from Epiphallogona only by the addi- 

 tion of the dart apparatus, the penis having exactly the same mor- 

 _ phology in the two groups. Now the simplest type of dart appar- 

 atus is that found in the genus Helicostyla, consisting of a sack con- 

 taining a needle-like dart, without crown or blades, and a simple, 

 mucus gland upon the dart sack, consisting of one layer of secreting 

 cells arranged radially around a central space or duct (see pi. 54, 

 fig. 7). This is, there can be no doubt, the primitive type of the dart 

 apparatus, from which the various elaborate forms of darts and 

 glands arose. No really primitive Belogona are now known to exist. 

 Helicostylais practically so in its dart arrangement, but it is diver- 

 gent in the loss of the flagellum (present in its Epiphallogonous 

 ancestors) and in the highly modified shell. 



The anatomy of the European types of dart-bearing helices has 

 been studied by Schmidt, Lehmann, Moquin-Tandon, and many 



