48 MALONE JURASSIC FORMATION OF TEXAS. [bull. 26H 
fine growth lines, of which some, occurring at short subregular inter* 
vals on the distal parts, are more strongly imbricated than others. 
Measurements. — Height, about 40 mm.; length, 38 mm. (plus 5?) : 
breadth, IT mm. 
Occurrence. — Known only by the above-described specimen, associ- 
ated with Get' ril li<t Cinderella, Exogyra potosina, Pleuromya incon- 
stans, etc. 
MYTILID^. 
Genus MYTILUS (Linn.) Brug. 
MYTILUS NUNT1US Sp. 11. 
PI. VI. figs. 4, 5. 
Shell small, equivalve (or slightly tortuous-inequivalve ? ) , rathen 
compressed, the right or left profile arched cuneate-oblong, consij 
erably less attenuated anteriorly than that of the somewhat similarlj 
proportioned recent species, M i/tilux <tfcr Gmelin, the angle made by 
the anterior margins of the cast being about three-fourths of a righ I 
angle; beaks terminal, subacute, gradually and moderately deflectJ 
upward, directed much more forward than upward; valves appal 
ently smooth or marked only with concentric growth lines. 
Measurements. — Length (oblique) of lateral profile, 21 mm. 
breadth of same, L0 mm.; breadth of shell, about 6 mm. 
Occurrence. — A single well-preserved cast, bearing thin remnant 
of the shell, was found among the Lower occurring fossils {Gervilll 
corrugata, Pleurotomaria circumtrunca, etc.) of the Theta U mile 
easl of Malone station. A form without trace of shell, observed oi 
the matrix of a Trigonia vyschetzkii from the same locality, probabj 
represents a valve of the same Mytilus and indicates for it a some 
what larger size. 
Though the longitudinal axis of this shell is arcuate, the archill; 
is -<> gentle that the outline approaches that of the straighter-profilei 
Mytilus afer, as figured by Tryon." more than one of such strongl; 
curved forms as sublcevis, < <1 uliformis, and decussatus. 
Genus MODIOLA Lamarck. 
MODIOLA MA no MAN A Sp. U. 
PI. VI, figs. 1, 2. 
Shell of moderate size in its genus, oblong-trapezoid, gently archec \ 
broade-t near the middle, the anterior and posterior regions rathe 
narrow and elevated, the height being greatest at or in advance of th 
posterior fourth; beaks small and only moderately elevated above th 
hinge line, placed close together, nearly or quite in contact anteriorly 
their dorsal summits forming rather narrow longitudinal ridges fror 
"Struct, and Syst. Conchol. 
