MITROMORPHA 65 
2 
Figs. 1,2. Protoconchs. 1. Mitromorpha (Mitromorpha) peaseana Finlay, Hawaiian Is. 
2. M. (Anarithma) metula (Hinds). Hawaiian Is. 
Kilburn’s (1986) diagnosis of the protoconch of species of the Mitrolumna group 
was “1!4-2 embryonic whorls”. However, the protoconch of M. (M.) olivoidea 
(Cantraine) has from 2-24 embryonic whorls and the same number can be found in 
M. (M.) alba (Petterd). Drivas & Jay (1986) described M. (M) kilburni as having 2'/ 
embryonic whorls and M. (M). keenae (Emerson & Radwin 1969), which is an 
undisputed Mitrolumna, has been described as having 3% smooth, glassy, 
translucent-white embryonic whorls (Emerson & Radwin 1969). This is clearly an 
overlap in the number of embryonic whorls between the Mitrolumnma group (1'A- 
3%) and the Anarithma group (2%4-4'4) of species. Paucispiral and multispiral 
protoconchs may be found in Vexillum s.str. Roding, 1978, Pusia Swainson, 1840, 
Nassarius Duméril, 1806, and the buccinid Cantharus (Prodotia) group, and a generic 
placement on features of protoconch characters would result in nomenclatorial chaos. 
For a list of synonyms of the genus-group Mitrolumna see Kilburn (1986). 
Subgenus Anarithma Iredale, 1916 
Anarithma Iredale, 1916, Proc.Malac.Soc.Lond. 12(1):27. Type species by M Clavatula 
metula Hinds, 1843. Recent, Indo-Pacific. 
Similar to both Mitromorpha and Mitrolumna in shell and radular features but 
differs from both in the convex columella with a “V”-shaped notch which resembles 
the columbellid notch in some Collumbellidae, siphonal canal notched. Operculum 
absent. Protoconch conical, consisting of 234-44 smooth embryonic whorls (Fig. 2). 
In addition to the species mentioned in more detail below, Columbella fischeri 
Hervier, 1899, also belongs to Anarithma. Columbella (Conidea) perplexa Schepman, 
1911, from the Moluccas, Indonesia is a synonym of M. (A.) fischeri and the species 
should be assigned to Anarithma rather than Lovellona as suggested by van Benthem- 
Jutting (1940). Hervier (1899) clearly mentions the “split-tooth” feature of the 
columella, a character which was not developed in the 3 immature examples of 
