194 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
PSEUDOBOLUS Cooper, new genus 
(Greek pseudes, false) 
Shells attaining a length of about an inch, oval in outline; subequally biconvex, 
the brachial valve having the greater convexity; pedicle beak elongated, in- 
curved. Greatest width in anterior third. Surface marked by concentric undu- 
lations and lines of growth. Interiors delicately marked by muscular and other 
impressions, but none could be identified as particular scars. Muscle platforms 
and septa wanting. 
Genotype.—Palaeoglossa gibbosa Willard (see below for reference). 
Discussion.—It is not usually wise to propose a genus for a species that does 
not reveal its internal characters because of the delicacy of their preservation, 
but this negative fact combined with a peculiar exterior may lend value to the 
genus. Pseudobolus in its attenuated beak and strongly convex valves is ex- 
teriorly unlike Obolus. Furthermore, its somewhat elongate oval form is another 
feature unlike Obolus. This form suggests assignment to Palaeoglossa, but 
reference to the type of that genus shows a fairly characteristic linguloid with 
somewhat attenuated beak quite unlike that of the genus under discussion. 
Furthermore, Lingula attenuata, type of Palaeoglossa, is strongly convex but 
is more like Lingula in its outline and presumably its profiles. 
Pseudobolus in exterior form is more like Dinobolus or Eichwaldia. The 
elongate beak and spacious, deep shells are reminders of the Trimerellidae, but 
no muscle platforms are present in either valve. Pseudobolus differs from Eich- 
waldia in not possessing the peculiar foramen so characteristic of that genus, 
and the brachial valve is nonseptate. 
A word about the shell structure of Pseudobolus is necessary to its under- 
standing. The shell seems to be laminated, but the lamellae are short and strongly 
oblique to the surface. The color is a dull whitish gray and not the usually lus- 
trous and highly colored brown or black common to Obolus and closely related 
shells. 
PSEUDOBOLUS GIBBOSUS (Willard) 
Plate 24, G, figures 26-31 
Palaeoglossa gibbosa WiLtard, Bull. Mus. Comp. Zool., Harvard Coll., vol. 68, No. 6, p. 256, 
pl. 1, fig. 3, 1928. 
Four specimens of this species are known besides the original type specimen. 
Only one is fairly well preserved ; it is a young individual but shows both valves 
in contact. The form and beak features of this young specimen taken together 
with the lack of detail in the interior of the other specimens suggest a new 
generic stock. 
The young specimen indicates a nearly equally biconvex shell with the brachial 
valve having the greater depth. In outline the shell is ovoid with the greatest 
width slightly anterior to the middle. Profile of pedicle valve gently convex; 
umbo well rounded, but anteriorly toward the anterior margin the shell is 
flattened perceptibly. Beak of pedicle valve long and slender and moderately 
incurved over the brachial beak. 
