2 14 



The scutum (PI. XXI, fig. 16, a and c) has distinct, but smooth lines of growth, a 

 well-developed articular ridge which is broadest in the middle and slopes towards the lower 

 extremity, and no adductor ridge. The cavity for the adductor muscle is slightly indicated. 

 Basi-tergal angle rounded. 



The tergum (PI. XXI, fig. 16, b and d) has the apex produced into a minute, sharp 

 point; scntal margin straight, spur broad; its antenor margin makes a hardly visible angle 

 with the scutal margin. The chitinous membrane which covers this valve bears quite a row ot 

 small yellowish hairs along the-carinal margin of the tergum. 



The very short remarks Darwin made regarding the structure of the animal's body 

 may be completed with the following: 



Mout h. Lab rum (PI. XXI, fig. 17): notch deep and narrow, not very wide at entrance. 

 Lateral margins forming an angle of about 90 with each other and a sharp angle with the 

 margin of the notch. Teeth small; in both the specimens examined by me, the sharp angle formed 

 by lateral margin and margin of the notch terminates, on both sides, in a sharp tooth, a 

 second one being situated close to the first in one specimen, and at a little distance from it in 

 the other. In the latter specimen a few more rudimentary teeth can be distinguished. A small 

 tuft of very short hairs is seen immediately below the larger tooth along the upper part ot 

 the margin of the notch. Shape of thickened portion of labrum almost rhombiform, its height 

 corresponding with its breadth. 



Palpi: elongate with the distal part growing narrower, and the extremity almost 

 pointed. Inferior margin only feebly convex, upper margin almost straight. A few longer hairs 

 only are scattered over inferior half of outer surface of the palpus, a dense row of shorter 

 hairs is disposed along upper margin and over inner surface, especially over its superior half. 

 Mandible (PI. XXI, fig. 18): distance between extremities of teeth 1 and 2 a little 

 longer than that between teeth 2 and 3. Tooth 3 slightly thicker-, teeth 2 and 3 indistinctly 

 doublé. Teeth 4 and 5 small but distinct; inferior angle terminates into 3 or 4 flat, short, 

 narrow, spine-like teeth. 



M ax il la (PI. XXI, fig. 19 and 19*): edge rather broad, shape of whole maxilla 

 triangular, pointed towards the extremity, where the place of attachment of the apodeme is 

 found. Upper pair of spines shorter than inferior pair. Between these pairs, 3 to 5 somewhat 

 shorter spines are disposed. Between the two spines at the basis a very small and narrow notch 

 is always observable. The notch behind the upper pair is small, yet distinct. (The one specimen 

 has 3 and 3, the other 4 and 5 intermediate spines). 



Outer maxillae (PI. XXI, fig. 20): have the outer lobe rather broad and quadrate, 

 with the upper extremity obliquely truncated, the lateral margins almost parallel. A large part 

 of the inner surface covered with hairs, most of which are directed in a direction at rioht angles 

 to the length of the maxilla. Inner lobe club-shaped, with the narrow part directed downwards. 

 Surface furnished with few, inner margin with not very numerous and somewhat longer hairs, the 

 strongest of which are directed to the basis of the maxilla. 



Cirri. First pair: has very unequal rami of 7 and 18 to 19 segments in the one, 

 and 6 to 7 and 19 to 20 segments in the other specimen. Segments of shorter ramus about 



86 



