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in the larger specimens and in the basal parts, is flattened laterally, which is caused by its 
being attached to the surface of a narrow object: the cirrus of a Pentacrinus. In some spe- 
cimens moreover, the shell is distinctly unsymmetrical. Neither the compartments, nor the 
radii have pores. The basis, which is represented by an extremely thin, calcareous layer (so 
thin and transparent that the structure of the surface of the cirrus of the Pentacrinus can 
be seen through it) also devoid of pores. 
Scutum (Pl. XXIV, fig. 5, @ and c). The growth ridges on the outer surface are very 
distinct, broad, not very numerous, hence the surface looks distinctly furrowed. Its apex is pointed. 
On the inner surface it shows no trace of an adductor ridge and no cavity for the adductor muscle ; 
the articular ridge, however, is prominent and extends over three quarters the length of the 
tergal margin. The cavity for the lateral depressor muscle is indicated, but only feebly developed. 
Tergum (Pl. XXIV, fig. 5, 4 and @). The general shape of the tergum is triangular, 
with the scutal margin straight, the carinal margin slightly arched, and the basal margin 
distinctly hollowed out. The basal margin merges imperceptibly into the exterior margin of the 
spur; the latter is rather broad and its anterior margin is separated only by a very short 
distance from the basi-scutal angle. In the larger specimens, the interior margin of the spur is 
almost confluent with this angle. Externally the surface is undulating: the part along the 
scutal margin and that along the carinal margin being separated from each other by a triangular 
middle part, which lies on a somewhat deeper plane. On the inner surface the articular ridge is 
long and well developed, and this is also the case with the crests of the depressor muscles. 
With regard to the structure of the animal’s body the following may be pointed out: 
Mouth. Labrum (Pl. XXIV, fig. 6 and 6*) without a central notch, a very shallow 
and rounded excavation being seen in its place. Teeth either small or not to be seen; in 
one of the specimens five small teeth could be made out on each side. Of the sub-triangular 
portion of the inner fold of membrane of the labrum, the basal margin can be seen as a 
crescent-shaped thickening, corresponding to the nearly horizontal chitinous list in other 
species of Lalanus. 
Palpi: of elongately-oval shape, with the free extremity rounded. The upper margin 
is nearly straight, the lower distinctly arched. A series of longer hairs disposed on the outer 
surface near the lower margin extend from the free extremity to about the middle of the palpus. 
Mandible (Pl. XXIV, fig. 7) with five teeth, regularly decreasing in size from the 
first to the fifth. Distance between extremities of teeth 1 and 2 about one and a half times 
the distance between 2 and 3. Teeth 2 and 3 with small additional teeth. A little tooth 
representing the lower angle is confluent with tooth 5. 
Maxilla (Pl. XXIV, fig. 8). A rather broad but shallow notch beneath upper pair 
of larger spines; edge beneath the notch slightly produced, armed with 4 to 5 somewhat 
shorter spines and the lower pair of longer ones. Numerous rather long hairs are seen 
between the spines, in the notch, beneath the lower pair, and round the lower angle. 
Outer maxillae (Pl. XXIV, fig. 9) with the outer lobe short and broad; hairs on 
that lobe very numerous, forming dense tufts at the free extremity and round the convex 
outer margin. Hairs disposed on the inner surface delicate; those along the inner margin and 
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