206 : CRETACEOUS GASTROPODA 
On the contrary, however, ascending through the orders of the Gastropoda 
from the ProsoBrRaANCHIA to the NEUROBRANCHIA and the PULMONATA we see, that 
the nearest resemblances between the animals and shells of the two last named and 
the first order are to be found almost exclusively among the Hoxtostomata. These 
are in fact more than simple resemblances, as we shall have occasion to notice in 
the family of the Rissoma and others, where transitions from marine to freshwater 
and terrestrial shells seem traceable with no great difficulty. Such series of changes, 
when, once they have been sufficiently studied and established by direct observation, 
will produce the most extensive alterations and improvements in our present defect- 
ive systematical arrangements. 
In a similar manner, as we have already done with the StpHonostomarTa, and 
in continuation of the last families of that tribe, we shall endeavour to arrange the 
families of the Hotostomata according to their respective affinities, and shall notice 
them in the following order :— 
21. Family —UELANIIDZ, (PAaLvpOMINe, MELANOPSINZ, MELANIINZ and 
STREPOMATINA). 
22. » —TURRITELLID. 
23. »  —SCALIDA. 
24. » —CACIDA. 
25. >»  —VERMETID A. 
26. » —SILIQUARIIDA. 
27. »  —ONUSTIDZ. 
28. »  —SOLARHDA. 
29. » —PLANAXIDZ (pravaxrvez and Liriopina). 
30. » —LITTORINIDZ (Lacouniné and Lirrorininz). 
3L. »  —AMPHIBOLIDA. 
32. »  —VALVATIDZ. 
33. » —AMPULLARIIDA. 
34. » —VIVIPARIDZ. 
35. » —RISSOHILIDA. 
36. s —RISSOID4 (with sub-families rrvncareLLIn&#, POMATIOPSINZ, 
BYTHINIINE, HYDROBIIN#, SKENEINZ, RISSOINE, RISSOININ# ), 
Bile 5 —HULIMID 42 (cxeunirziuns, EVLIMINA and STYLIFERINA). 
38, - —NA TICID4i (TYLostoMiIne, NATICINA and SIGARETINE). 
39. » —VANIKORIDE. 
40. » —VELUTINIDA. 
41. » —IANTHINIDA. 
42. » —CALYPTRIDA. 
43. » —CAPULIDA. 
4A., » —LECTURIDA. 
45. »  —GADINIDZ. 
46. » —LHPETIDA. 
AT. » —SIPHONARITD. 
