THE ANNALS 
MAGAZINE OF NATURAL HISTORY. 
[THIRD SERIES.] 
No. 98. FEBRUARY 1866. 
VIII.—Conchological Gleanings. 
By Dr. E. von Martens. 
I. On the Subdivisions of the genus Pinna. 
Cuemnitz, in his well-known work ‘Conchylien-Cabinet ’ 
(vol. viii. 1785, p. 197), represents the inside of two species of 
Pinna, in order to show, as he expresses himself, the shape of 
the muscular impressions and the singular outlines of stripes 
(sonderbare Zeichnung von Streifen) which are to be seen 
in some species on the inside of the apices. In the one, fig. A, 
Pinna incurva, Gmel., a median straight line is to be seen; 
in the other, fig. B, P. nigrina, Lam., no trace of it. 
Lamarck observed in a fossil species, which he therefore 
named P. subguadrivalvis, that the median line of each valve is 
elevated into an edge and cleft (“ valvarum angulo dorsali longi- 
tudinaliter fisso’’). 
Dr. J. E. Gray established, as early as 1840, the genus Atrina 
for P. nigrina, in the ‘Synopsis of the Contents of the British 
Museum,’ but without stating anything about the characters of 
the new genus. 
Mérch (Catalogue of the Collection of Yoldi, 1853, p. 51) 
distinguished four genera—Pinna, Cyrtopinna, Pennaria, and 
Atrina—also without any indication of the characters. 
H. & A. Adams (Genera of recent Mollusca, vol. 1. 1858, 
p- 529) mention, in the general description of Pinna, that the 
“apical portions are sometimes longitudinally fissured, and the 
fissure filled up with cartilage ;” they admit Aérina as a sub- 
genus, and define it in the following words: ‘Shell with the 
apical portions of the valves entire.’ Consequently they seem 
to regard the fissure as characteristic of the subdivision of the 
true Pinne. 
My attention was drawn to this subject by Mr. Sadebeck, 
assistant at the Paleontological Collection at Berlin, who showed 
me a fossil Pinna from the Jura formation (P. granulata) in 
Ann. & Mag. N. Hist. Ser. 3. Vol. xvii. 6 
