2^1 



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 Pentacriniis can 

 be seen through it) also devoid of pores. 



Scutum (PI. XXIV, fig. 5, a and c). The growth ridges on the outer surface are very 

 distinct, broad, not very numerous, hence the surface looks distinctly furrowed. lts apex is pointed. 

 On the inner surlace it shows no tracé 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 (PI. XXIV, fig. 5, b and d). 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 

 midclle 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: 



Mout h. Lab rum (PI. 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 Balamis. 



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 (PI. 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 (PI. 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 maxi 11a e (PI. 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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