ANIMALS. 167 
two to five, according to species), as in Perna and Gervilia; and it possesses anterior 
and posterior linear teeth,’ similar to those of the Cucullzea-toothed Arks.”” 
Until more is known of the general characters and chronogeny of a number of 
paleozoic fossils apparently belonging to Plerinea, Goldfuss, Actinodonta, Phillips, 
Modiolopsis, Hall, Myalina, Koninck, and some undescribed genera, it is impossible to 
speak with any safety as to the affinities of the present genus, or even the family which 
it typifies. “ Bakevellia appears to be related to Perimea; but the latter has no 
cartilage-pits:” its resemblance to Avicua is purely simulatory. 
BAKEVELLIA CERATOPHAGA, Schlotheim. Plate XIV, figs. 24, 25, 26, 27. 
MyrtiLites KERAToOPHAGUS, Schl. Akad. Miinch., vol. vi, p. 30, pl. v, fig. 2 a, 6, c, 1816. 
— CERATOPHAGUS, ,, Petrefactenkunde, p. 293, 1820. 
— — »  Boué, Edin. Phil. Journ., vol. xii, p. 144, 1825. 
AvicuLA—striated sp., which resembles a Gervillia, J. de C. Sow. Trans. Geol. Soc. 
Lond., 2d series, vol. ii, p. 119, 1829. 
MyriLus KERATOPHAGUS, Schl. De la Beche, Geol. Man., Germ. Transl., p. 459, 1832 ; 
3d Eng. Ed., p. 573, 1833. 
— ? — », Phillips, Encye. Met., vol. iv, p. 617, 1834. 
AVICULA CERATOPHAGA », Goldfuss, Petrefacta, 2d part, p. 126, pl. 116, fig. 6. 
—  KERATOPHAGA », Geinitz, Geea von Sachsen, p. 96, 1843. 
— — », De Verneuil, Bull. Soc. Géol. de France, 2™° série, t. i, 
p. 33, 1844. 
— — », Geol. Russ., vol. i, p. 224, 1845. 
— — », Geinitz, Grundriss, p. 457, 1846. 
—_ — » Tennant, Strat. List, p. 88, 1847. 
BAKEVELLIA CERATOPHAGA ,, King, Catalogue, p. 10, 1848. 
AVICULA KERATOPHAGA » Howse, Trans. T. N. F. C., vol. i, p. 249, 1848. 
GERVILEIA  — », Geinitz, Versteinerungen, p. 10, pl. iv, figs. 16, 17, 1848. 
Diagnosis.—‘“‘ Shell subrhomboidal, arched, the front wing rounded, the one behind 
falciform produced, with regular concentric lines.’” 
Bakevellia ceratophaga is so truly like an Avicala, in its long hinge-line, slight 
umbonal divarication, prominent incremental lines, long posterior wing, anterior lobe, 
and byssal or pedal sinus, that Schlotheim, who published some excellent figures of it, 
was struck with its “resemblance to young specimens of J/ytilus hirundo, Linn.”* 
It is somewhat variable in form; but its distinctive characters are easily recognised 
in the line of separation, between the convexity of the upper or large valve and the 
area of the wing, being abrupt, well defined, and slightly oblique to the cardinal line; and 
1 Vide Plate XIV, fig. 34. 
2 King, Catalogue, p. 10. 
3 * Avicula testa subrhomboidali fornicata, ala antica rotundata postica falciformi producta, lineis con- 
centricis regularibus.”’ (Goldfuss, Petrefacta, 2d part, p. 126.) 
4 Denkschriften der Koniglichen Akademie zu Miinchen, vol. vi, p. 30. 
