APPENDIX. 349 
from the second) Prof. Gill uses the name Rhipidoglossa, char- 
acterized by the development of numerous hooklets or uncini 
upon either side of the central and few lateral teeth of the lingual 
ribbon (vol. i, Pl. xii, f. 43-50). But this character is not coex- 
tensive with the order Scutibranchiata, although nearly so, and 
is besides of doubtful importance. Rather than use it in combi- 
nation with a modification of the extent and characters of the 
Scutibranchiata, I prefer to suppress that order entirely, as 
Fischer has done, and as I originally intended to do (vol. i, 
p. 82). 
In the case of Helicina, which possesses the dentition and 
form of shell of the scutibranchs, there is an external sexual organ 
in the male, thus allying it with typical pectinibranchs. This 
and the other land mollusks provided with opercula, and in 
which the branchizw are represented by a network spread upon 
the walls of a pulmonary chamber, are by some systematists 
made a separate order, Pheumonopoma, connecting the pectini- 
branchs with the Pulmonata; they are closely connected through 
Ampullaria, etc., as well as by their opercula and bisexuality, 
with the former. 
The second suborder of scutibranchs, the Edriopthalme, are 
distinguished from ordinary pectinibranchs by their conical 
shell, but vary greatly among themselves in dentition (the 
Patellidz, etc., being docoglossate (vol. i, Pl. xii, f. 51), and 
in the form and position of the branchie (vol. ii, 326, 329, 330, 
331, 332). 
The limits of the order Pectinibranchiata should be enlarged 
to include the non-spiral shells and variously situated gills of the 
limpets, and the aberrant, pneumonopomous, operculated terres- 
trial mollusks. 
I annex Fischer’s classification : 
Class Gastropoda, 
Subelass Univalvia. 
Androgyna. 
Order 1. Pulmonata. 
Order 2. Opisthobranchiata. 
Dioica. 
Order 3. Nucleobranchiata (Heteropoda). 
Order 4. Prosobranchiata (Platypoda). 
Subclass Multivalvia. 
Order 5. Polyplacophora. 
CoLuMBELLA, Lam. lp. 178]. 
MITROLUMNA, Bucq., Dautz. et Dollf., 1883. Proposed for a 
group of shells uniting the characters of Mitra and Columbella: 
no operculum. Type, Columbella Greci, Phil. Mediterranean. 
