E. Rolan & H. G. Lee 
Novapex 13(1): 43-44, 10 mars 2012 
Rissoina parkeri (Mollusca: Rissooidae): a curious Caribbean species 
of uncertain status 
Emilio ROLÂN 
Museo de Historia Natural, Campus Universitario Sur 
15782 Santiago de Compostela, Spain 
Harry G. LEE 
4132 Ortega Forest Drive 
Jacksonville, FL 32210-5813, USA 
KEYWORDS. Gastropoda, Rissoina , Grand Cayman, Caribbean. 
ABSTRACT. Two shells of a Rissoina with planktotrophic development found in Grand Cayman, 
show the problematic of its diagnosis. 
Recently malacologist David Kirsh collected two 
specimens of a Rissoina in the waters of Grand 
Cayman Island. Each shell possess a planktotrophic 
protoconch (Figs 1-3) which character is not 
consistent with any known congener from the 
Caribbean (see Rolan & Fernândez-Garcés, 2010). 
The shells are coincident in size and sculpture with 
the figure and description of Rissoina parkeri , but 
hâve one more teleoconch whorl than the holotype of 
that species. This can explain why these two shells are 
a little larger (6.2 and 6.0 mm) than the holotype (4.4 
mm). 
Olsson & Harbison (1953: 327-328, pl. 48, fig. 5) 
described the fossil species Rissoina parkeri from 
Shell Creek, Florida, USA. The type specimen is a 
little immature, with the lip not fully developed. It was 
deposited in ANSP (19434). 
In the searchable database of the Florida Muséum 
of Natural History (FLMNH) there is a shell with 
Catalog Number 26545 from Glades County, Neogene 
of Florida. 
On the Internet database Malacog 4.1.1 
(Rosenberg, 2009) R. parkeri is tentatively treated as a 
synonym of Rissoina krebsii (Morch, 1876). However, 
on examination of these two species it is évident that 
the latter (Fig. 5) has more ribs and spiral cords and, 
most important perhaps, a paucispiral protoconch (Fig. 
6). Another similar species is Rissoina multicostata 
(C.B. Adams, 1850) (Figs 7-8), which likewise has 
many more ribs and cords but a paucispiral 
protoconch (FigT 9). 
The only problem is that the species R. parkeri 
was considered a fossil while the two Kirsh shells 
hâve the appearance of Recent mollusks. Given a 
protoconch of more than 2 Vi whorl s, one must 
présumé that if it is a Recent species it would be 
known from other countries in the Caribbean and this 
is not presently the case. 
Another possibility is that this material, despite 
bearing the appearance of Recent shells, may be from 
a submarine Quarternary deposit. 
Acknowledgements 
The scanning électron micrographs were made by 
Jesüs Méndez in the Centro de Apoyo Cientifico y 
Tecnolôgico (CACTI) of the University of Vigo. To 
David Kirsch for the loan of the specimens studied. 
REFERENCES 
Olsson, A.A. & Harbison, A. 1953. Pliocène Mollusca 
of Southern Florida, with spécial reference to those 
from North Saint Petersburg. Monographs of the 
Academy of Natural Sciences of Philadelphia, 8: 
vii + 459, 65 pis. 
Rolan, E., & Fernândez-Garcés, R. 2010. New 
information on the Caribbean Rissoina 
(Gastropoda, Rissoidae) of the group R. 
sagraiana-cancellata, with the description of a 
new species. Iber us, 28(1): 79-89. 
Rosenberg, G. 2009. Malacolog 4.1.1: A Database of 
Western Atlantic Marine Mollusca. [WWW 
database (version 4.1.1)] URL 
http://www.malacolog.org/ . 
Specifically: 
< http://www. malacolog.org/search. php?syns : =Show+S 
vnonvms&showsvnonvms=true&mode=wheresearch 
&wherebit=+and+(+w.originalgenus+%3D+'Rissoina , 
++or+w.currentfullname+like+ , Rissoina+%25 , +or+w. 
originalcombination+like+ , Rissoina+%25'+or+w.origi 
nalcombination+like+ , %25(Rissoina)%25')++ > 
43 
