302 
margin. Carina almost keeled, forming an acute angle seen from 
above. Scuta large, with distinet ridges of growth and radially ar- 
ranged groves; terga all but invisible in closed specimens. Rostral 
compartment consisting of three coalesced, but distinetly evident 
plates. 
The six com partmen ts are easily distinguishable owing to the 
well developed, triangular alae (Fig. 48) which are developed along 
the carina, the carinal latus, and the median latus. The compart- 
Fig. 48. Pachylasma scutistriata from 38° 12’ S., 149 o 40’ E. Type specimen in side 
view, and from above. [X 1,5]. 
ments are vividly pinkish, not seldom with vertical darker, and 
lighter stripes radiating from the apex of the compartment; the 
alae, on the other hånd, are only feebly coloured or almost quite 
white and thus very conspicuous as against the compartments. The 
lines of growth are often almost invisible, and very irregular in 
the compartments, but sometimes they may be somewhat accent- 
uated by their colour and more regularly arranged. In the alae 
the lines of growth are regular and distinet, parallel with the margin. 
The sheath has very regular, and well developed lines of growth; 
the basal part of the compartments has an inner all but porcel- 
laneous surface. No pores are present. 
In young specimens the basis is membraneous. In larger spec¬ 
imens, on the other hånd, the outer parts of the basis are cal- 
cified, whereas the central part remains membraneous. The calcifi- 
cation is rather intense, and the calcified parts of the basis in old 
specimens attain a fairly conspicuous thickness. 
The carina is not very broad, and has a pointed apex; the 
broad alae form a pointed angle with each other, and the plate is 
therefore narrowly V-shaped in transverse section, especially in its 
upper part. 
