26 
PACIFIC SCIENCE, Vol. XXI, January 1967 
In dorsal view: carapace inflated, greatest width 
at subcentral swelling and posteroventral exten- 
sion; broad inconspicuous central sulcus present; 
caudal process relatively compressed; anterior 
blunt, with two smooth marginal ridges per 
valve, converging at anterodorsal angle. Orna- 
mentation heavy, complex, distinctive, of dis- 
tinct or coalescing heavy knobs and ill-defined 
ridges with general horizontal trend, adjacent 
depressions partially filled with secondary (?) 
growth; marginal ridge of ventral inflation ex- 
tending around anterolateral surface to well- 
defined eye tubercle, paralleling outer anterior 
marginal ridge. 
Hingement essentially holamphidont: ter- 
minal teeth of right valve entire (posterior tooth 
faintly trilobed) ; median bar of left valve 
heavy, smooth anterior tooth entire. 
Adductor muscle scar pattern four in a row 
on side of deep pit, second and bottom scars 
divided into two scars; two antennal scars, one 
above the other, deep within pit; single man- 
dibular scar just dorsal to pit. Radial pore 
canals very abundant, straight, single, many in 
anterior with midswellings; no vestibules pres- 
ent; normal pore canals large, sparse; flange 
in left valve and flange groove in right valve 
heavy, well developed. 
dimensions: 
SPECIMEN 
LENGTH 
WIDTH HEIGHT 
Holotype usnm 648762 
(entire 9 ?) 8-23 
/ 
0.64 
0.37 
0.39 
Paratype sdnh 1045 
(right valve $ ?) 
. S-23 
0.63 
0.18 
0.39 
Paratype usnm 648763 
(left valve $ ?) 
S-23 
0.67 
0.19 
0.40 
Paratype usnm 678764 
(entire $ ?) AR 
0.65 
0.41 
0.37 
Paratype sdnh 1046 
(entire $ ?) AR 
0.67 
0.44 
0.40 
DISTRIBUTION : As 
fossils 
from 
S-23 (4 
valves; 1 entire) AR (2 valves; 2 entire). 
discussion: Aspects of shape, ornamentation, 
and musculature of this species are not typical 
of others in the genus; for this reason the 
generic assignment is questioned. Two forms 
occur in the collection, differing only in the 
degree of development of ornamentation. Spe- 
cimens illustrated in Figures 17 a-d from sta- 
tion S-23 possess relatively heavier ridges than 
those in Figures 17 e—f from station AR. These 
differences are not considered to be of specific 
importance, however. 
Brady’s species of Cythere jungoides (1880: 
pi. 19, fig. 7) is similar in shape to Mutilus (?) 
coalescens although they differ in ornament. 
Unfortunately, the internal features of C. 
fungoides are unknown and the relationship 
between these two forms is obscure. 
Genus Jugosocythereis Puri, 1957 
Jugosocythereis venulosus n. sp. 
Figs. 18 a-c 
diagnosis: Carapace short, inflated; orna- 
mentation of small reticulations aligned in 
stripes; subcentral tubercle pitted (without the 
ridges which are typical of the genus). 
description: In lateral view: dorsal margin 
straight to slightly convex with small central 
hump ; ventral margin straight, curving upward 
abruptly at posterior, ending at weak, pointed 
caudal process ; posterodorsal margin weakly 
concaved above caudal process; anterior margin 
blunt, smooth, evenly rounded. In dorsal view: 
carapace tumid, about as wide as high; equally 
wide at subcentral and posteriorly directed 
posteroventral tubercles; prominent posterodor- 
sal tubercle present; margins smooth save for 
some inconspicuous wide spines in postero ven- 
ter; left valve larger and strongly overlapping 
right valve above terminal hinge elements ; orna- 
mentation unique: deep pits coalescing into 
narrow horizontally trending furrows, giving 
shell a striped appearance; eye tubercle broad, 
deep-set, with postjacent prominent pit. 
Adductor muscle scar pattern partially ob- 
scured ; one of middle scars divided ; two 
antennal scars on anterior side of pit, large 
mandibular scars above subcentral pit, double 
mandibular scar below pit. Anterior and pos- 
terior vestibules narrow; radial pore canals ob- 
scure, apparently straight and simple, with some 
midswellings ; normal pores small, sparse. 
Hingement probably hoi- or hemiamphidont 
dimensions: 
SPECIMEN 
LENGTH 
WIDTH 
HEIGHT 
Holotype usnm 678765 
(entire) T-12 
0.61 
0.36 
0.39 
Paratype sdnh 1047 
(right valve) T-12 
0.62 
0.17 
0.36 
Paratype usnm 648766 
(entire) T-12 
0.61 
0.35 
0.36 
