THE NAUTILUS 101(2):59-68, 1987
Page 59
A Revision of the Seguenziacea Verrill, 1884
(Gastropoda: Prosobranchia). II. The New Genera
Hadroconus, Rotellenzia, and Asthelys
James F. Quinn, Jr.
Florida Department of Natural
Resources
Bureau of Marine Research
100 Eigfitfi Ave.. S.E.
St. Petersburg, FL 33701, USA
ABSTRACT
Three new genera of the superfamil\ Seguenziacea are pro-
posed, Hadroconus is erected for two western Atlantic and one
western Pacific species formerly assigned to Basilissa Watson,
1879. Another species, Basilissa larnpra Watson. 1879. is here
made type-species of the monotvpic genus Rotellenzia. One
specimen from the syntype series of Carenzia carinata (Jef-
freys, 1877) from the North Atlantic Ocean is a juvenile of
Basilissa munda Watson, 1879, which is here established as
type-species of Asthelys new genus; Basilissa simplex Watson,
1879, is also assigned to this genus. Shells of Hadroconus alius
(Watson, 1879). Rotellenzia larnpra (Watson. 1879). and Asthe-
lys munda (Watson, 1879), are described and illustrated b\
SEM micrographs and/or light photographs. Comments on util-
ity of shell and radular characters for generic definitions are
presented.
INTRODUCTION
The systematics of the Seguenziacea Verrill, 1884, has
undergone extensive examination and revision during the
last 5 years. Prior to 1983, only six valid genera had been
established. An equal number of new genera were erect-
ed in 1983 [Marshall. 1983 (5); Quinn, 1983a (1)]. Sub-
sequent research on the western Atlantic fauna has re-
vealed two additional genera, and examination of the
unique specimen of Basilissa larnpra Watson, 1879, makes
a third new genus necessary.
In a previous paper (Quinn, 1983b), I noted that shell
characters were useful in distinguishing between taxa
and, in most cases, were the only characters available at
the species and genus levels. For example, differences in
size of protoconch, number and distribution of primary
and secondary sculptural elements (e.g., spiral carinae,
cords, threads, collabral riblets), features of the intersec-
tion of the sculptural elements (e.g., nodulose or smooth,
sharp or rounded nodules, laterally compressed or not),
t\pe of columellar tooth, etc., are important in species
discriminations. Some characters, especially shell pro-
portions, may or may not be adequate for species dis-
tinctions and must be evaluated on a case-by-case basis.
Ideally, delimitations of genera should entail analyses
of shell, radular, and anatomical characters. That ideal
is hampered in the Seguenziidae by lack of material
available for dissection (see summary in Quinn, 1983b).
As a result, all genera have been established principally
on the basis of subjective evaluations of shell features,
sometimes augmented by a description of the radula.
Despite this approach, with the attendant potential for
unnecessary generic splitting, authors prior to 1970 \\ ere
very conservative in erecting new genera. In three recent
papers (Vlarshall, 1983; Quinn, 1983a, b), generic con-
cepts of seguenziids have been refined, again based prin-
cipally on conchological characters, but no author has
presented a discussion of shell characters that, when used
in combination, are useful in delimiting genera. I take
the opportunity to do so here.
Shell shape: With few exceptions, shell shape gives a
good first approximation of generic placement. The fol-
lowing definitions of shell shape w ill be used in this and
subsequent papers; (1) conical
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