374 
THE CORAL TRIANGLE: HEARST BIODIVERSITY EXPEDITION 
Description. — External morphology: The living animals (Figs.lG,H) are narrow and elon¬ 
gate, 3 to 13.5 mm in length and about 4 mm wide in the largest specimens. The cephalic shield is 
two to three times the length of the posterior shield. The parapodia are extremely short (Fig. 11 A), 
and narrow, barely reaching the cephalic shield, and leaving the anterior and posterior shields 
entirely visible. The posterior end of the posterior shield is blunt and has a pair of elongate exten¬ 
sions. The gill is simply plicate consisting of five primary folds and is situated venti'ally on the right 
posterior end of the animal. 
The body color of the living animal is uniformly translucent white with opaque white speck¬ 
ling over the surface of the animal. The opaque white pigment of the gizzard plates is visible 
through the translucent body, as is the golden brown pigment of the shell. 
Shell (Fig. lOD): The shell is wide and open with a thickened posterior margin, where it occu¬ 
pies the majority of the posterior shield. 
The shell lacks sculpture but growth lines are evident over its surface. The posterior flange is 
elongate with a series or irregulai* denticles along the margin. 
Digestive system (Fig. 10): The buccal mass is large and elongate, occupying the anterior two- 
thirds of the anterior shield. The buccal bulb has a relatively small radula. The radular formula in 
one paratype specimen (CASIZ 163775) is 18-21 x 1.0.1. The inner lateral teeth (Fig. IOC) are 
large and broad with a curved prominent cusp. Their masticatory margin has a series of up to 52 
elongate, closely crowded denticles. Outer lateral teeth are absent. There is a large ventral oral 
gland and small dorsal oral glands. At the posterior end of the buccal mass, near the junction with 
the crop, is a pair of short salivary glands. The gizzard is large and highly muscular, much wider 
than the buccal bulb. There are three unequally-sized gizzard plates that are elongate with round¬ 
ed apices. The unpaired plate (Figs. 1OA, D) is smaller than the two paired plates (Fig. 10B,D). The 
central region contains two pores, one that is larger and more elongate and a smaller one that is cir¬ 
cular (Fig. lOD). The two paired plates differ in size (Fig. lOD) and each of them has only a sin¬ 
gle elongate pore. There is organized pattern of fine honeycombed microscopic network on the giz¬ 
zard plates, although it is not well organized. The gizzard narrows posteriorly and enters the diges¬ 
tive gland. The intestine emerges from the right side of the digestive gland and terminates near the 
posterior end of the body near the base of the gill. 
Central Neiyous System (Fig. IIB): The circumesophageal nerve ring consists of paired cere¬ 
bral, pedal and pleural ganglia and a single supraintestinal ganglion immediately posterior to the 
right pleural ganglion. The cerebral and pedal commissures are both somewhat elongate with well- 
separated respective ganglia. On the ventral side of the buccal mass near the entrance of the esoph¬ 
agus are the buccal ganglia, which are immediately adjacent to each other. From the posterior end 
of the anterior nerve ring the right branch of the visceral loop the osphradial nerve extends poste¬ 
riorly from the supraintestinal ganglion. The two lateral branches of the visceral loop join posteri¬ 
orly at the posterior ganglia. The left visceral loop enters the subintestinal ganglion, while the right 
lateral nerve enters the visceral ganglion. The visceral ganglion is larger than the subintestinal gan¬ 
glion. From the visceral ganglion is the genital nerve, which does not appeal* to have a distinct gen¬ 
ital ganglion. 
Reproductive System (Figs. IIC-D): The arrangement of reproductive organs is essentially 
monaulic (as discussed by Gosliner 1994) but with a single branch of the hermaphi*oditic duct to 
the albumen and membrane glands (Fig. 11C). From the large ovotestis, which is intenningled with 
the digestive gland, emerges the wide, convoluted ampulla. The ampulla narrows considerably. 
After the hennaphroditic duct crosses over the receptaculum seminis, it widens and curves around 
the distal surface of the pyriform receptaculum. The duct completes a circle around the receptacu¬ 
lum and branches to the albumen and membrane glands and also receives the duct of the receptac- 
