305 
ments on the other hånd, show the same arrangement of spines 
as the three posterior cirri. 
The caudal appendages are a little longer than the proto- 
prodite of cirrus VI, and have 15 to 18 segments; only the distal 
segments have some few and well developed hairs. 
The penis is only little longer than the protopodite of cirrus 
VI, stout, and annulated all over. Some few and small hairs are 
scattered on its surface, and at the distal end it has two lateral 
tufts of long and strong hairs. 
The species at hånd comes near to Pachylasma Darwinianum 
Pilsbry (1912); the latter has an entirely membraneous basis, and 
the present species thus bridges the gap between Pachylasma Dar¬ 
winianum and the typical Pachylasma-speciQS with their more com- 
pletely calcified bases in adult specimens. The species with mem¬ 
braneous bases moreover link Hexelasma to Pachylasma, and leave 
a sound base for a separation of these genera. The other character, 
which consists in the presence, resp. absence of caudal append¬ 
ages, also fails. According to Pilsbry (1916) the caudal append¬ 
ages in Pachylasma Darwinianum consist of „only one extremely 
minute joint“, i. e. they are quite rudimentary. In Pachylasma scu- 
tistriatum the appendages are, on the other hånd, among the best 
developed in the genus counting up to 18 segments, and thus al¬ 
most reaching the same number as in Darwin’s (1853) spec¬ 
imens of Pachylasma giganteum (Philippi) which had 19 segments. 
Between these extremes the other species hold intermediate pos¬ 
itions. 
Pachylasma scutistriatum also comes near to Pachylasma crinoi- 
dophilum Pilsbry (1911), but differs in the width of the carino- 
lateral compartment; this is in the latter species half as wide as 
the lateral (mediolateral) compartment, in Pachylasma scutistriatum , 
on the other hånd, of the same width as the lateral compartment. 
Genus Chtamalus Ranzani. 
Chtamalus autenvatns Darwin. 
Port Hacking, N. S. W., on the beach. 10/X 14. Several large specimens 
together with Tetraclita squamosa. 
Vidensk. Medd. fra Dansk naturh. Foren. Bd 73. 
20 
