Thoracic Cirripedia from a Guyot— Zullo and Newman 
357 
tion of the carinal margin and are marked by 
chevron-shaped growth lines; primordial valves 
apical; interior moderately concave, smooth; 
scuto-occludent angle with fossa to receive pro- 
jection formed by tergo-occludent angle of 
scutum. 
Scuta (Figs. 2 A, B, C—2 ) broadly triangular, 
divided into two portions by a ridge running 
from the umbones to the tergolateral angles; 
exterior marked by distinct growth lines running 
transversely above, and nearly longitudinally be- 
low the dividing ridge; minute ridges running 
perpendicular or nearly perpendicular to them; 
surface above dividing ridge broadly convex; 
below ridge, reflexed outwards laterally to form, 
with its neighbor and the expanded basal por- 
tion of the carina, a receptacle for the peduncle; 
interior smooth, broadly concave; elevated oc- 
cludent margin terminating in a smooth articular 
surface at the umbo; portion basal to umbo 
forming ventrolateral elements of peduncular 
receptacle; carinal margin supporting shallow 
fossa in lower third, receiving lateral tooth of 
carina; umbo situated approximately one-fifth 
the length of the occludent margin of the scutum 
from the base; faint scar of the strong scutal 
adductor muscle located just inside the ridge of 
the occludent margin opposite the tergolateral 
angle. 
Carina (Figs. 2 A, B, C- 3, D ) indistinctly 
divided into two regions due to expansion and 
flection of basal portions in forming the carino- 
lateral elements of the peduncular receptacle; 
external surface of basolateral portions support- 
ing about six rows of short, small, weak ridges; 
entire valve crossed by longitudinal growth 
lines running nearly parallel to the scutal mar- 
gin; carinal margin with chevron-shaped growth 
lines running into a shallow V-shaped trough or 
depression; this depression not continued for- 
ward onto the carinal ridge formed by the 
carinal margins of the terga; primordial valve 
occasionally supported on a projecting umbonal 
portion (cf Figs. 2 B, D); this arrangement 
apparently not correlated with size in the dozen 
specimens examined, as suggested by Barnard 
(1924); inner cup-shaped plate, along with 
expanded lateral portions, forming carinal con- 
tribution to the peduncular receptacle, produced 
laterally as a pair of teeth; distal angles flared 
laterally, forming articular surfaces on which 
the terga and scuta bear; capitulum of holotype 
UCMP 37860, the largest specimen, measured 
9.5 mm high, 3.8 mm deep, and 3.6 mm wide; 
peduncle had average diameter of 1.2 mm and 
extended 0.82 mm below basal margin of carina; 
orange ovigerous lamellae visible through semi- 
translucent shell; smallest specimen in series 3 
mm high. 
Labrum (Fig. 2 E) produced anteriorly in a 
V-shaped trough, divided into right and left 
portions by a medial ridge in the chitin; sup- 
porting 22-24 small, stout, sharp teeth; man- 
dibular palps spatulate, attached to labrum; 
superior margin slightly concave, supporting 
numerous spines along superior and inner mar- 
gins (left palp in Fig. 2 E aberrant); mandible 
(Fig. 2 F) remarkably long, with four teeth, not 
including inferior angle; inferior angle bifid; 
surface clothed with short spinules, a few of 
which extend over cutting edge; superior and 
inferior margins and notch between first and 
second teeth supporting long spines; inner 
maxilla (Fig. 2 G) with three major spines above 
and many below notch; notch, and superior and 
inferior margins, supporting several spines; sur- 
face clothed sparsely with degenerate spinules 
occurring in groups of one to four; outer maxilla 
(not figured) nearly one-third again as long as 
high; superior margin slightly concave; superior 
and inner margins supporting long, relatively 
heavy setae or spines. 
Cirrus I widely separated from II; attached to 
posteroventral margin of prosoma; rami sub- 
equal; outer ramus approximately twice as wide 
as inner ramus, setae arranged nearly symmetri- 
cally on both lesser and greater curvatures; 
terminal article supporting about six strong 
spines; inner ramus densely setose on lesser 
curvature, a few spines at each articulation on 
greater curvature, articles slightly longer than 
wide; setal arrangement essentially ctenopod 
and normal in appearance; remaining cirri 
clearly ctenopod; each cirrus in turn longer than 
the preceding; rami subequal; proximal articles 
(except the first) nearly as long as wide; inter- 
mediate articles nearly 4 times as long as wide, 
each with five pairs of setae, the two or three 
stronger pairs pinnate; first proximal article 
long, apparently composed of several fused seg- 
ments; pedicles of all cirri supporting a single 
row of minute spines along posterior margins 
