1941] 
Sumatran “Trilobite Larva” 
27 
ones at the posterior margin near the middle; abdominal 
tubercles very small, transverse, arranged in pairs near the 
middle of the hind margin of each of the basal six tergites, 
but these are lacking on the last three tergites. Lateral 
horns or processes on the abdomen long; except the first, 
all are curved backwards, but not upwards; those of the 
Fig. 1. Ventral view of abdomen of Sumatran “Trilobite” larva. 
last tergite short, simply extending its lateral angles ; those 
of the first short and pointed at tip, the others blunt. On 
the underside the meso- and metasternum each bear a 
minute, convex tubercle at the center. Each abdominal 
sternite with a tooth-like projection on each side at the pos- 
terior angle. Each of the pleurites, which lie directly below 
the lateral processes of the terga, is produced at the posterior 
angle into a blunt tooth and each is perforated by a deep, 
circular, spiracular opening. The two spiracles of the thorax 
are similar and lie at the anterior margin of the meso- and 
