292 
case in two out of three instances: in 50 specimens taken at hap- 
hazard 32 had their left scutum and tergum movable, in the other 
18 specimens the left scutum and tergum were fixed, the right 
tergum and scutum being movable. 
Also the sculpturation of the plates exhibits great variations. 
In most specimens radiating ribs are rather prominent in the mov¬ 
able scutum and tergum as also in the rostrum; in some spec- 
Fig. 40. Verruca albatrossiana, 25 miles E. of Zamboanga. a specimen showing no 
radiating ribs in tergum and scutum, half from above, b common, strongly sculptured 
specimen, half from above, c the same specimen in side view, rostrum left, d the 
same facing the fixed tergum and scutum, tergum left, c outlines of the same spec¬ 
imen, carinal view (c carina, r rostrum, ft fixed tergum, s and t movable scutum 
and tergum), f interiør side of right scutum and tergum. [All figures X 4]. 
imens the radiating ribs have entirely faded away with exception 
of the diagonal rib, and the articular ribs, and only the transverse 
ridges of growth are prominent as in the other plates. Between 
these two extremities every transition is present. 
Generally four articular ridges are present in the tergum; some- 
times the marginal ridge exhibits a median longitudinal furrow in 
the lower part thus giving origin to a fifth articular ridge. — The 
vertical ridges of the parietal areas of the wall vary greatly in 
numbers. 
The size of the greater specimens coincides with the dimens¬ 
ions quoted by Pilsbry (1912). 
Verruca cristallina Gruvel. 
25 miles E. of Zamboanga, 250 fathoms. 4/III 14. Four specimens of 
forma laevis nov. on large spicules of a siliceous sponge. 
