52 BULLETIN 82, UNITED STATES NATIONAL MUSEUM. 



AXTEDON MEDITEPRANEA. 

 Fig. 79, p. 53. 



The radial articular faces of this species differ but very slightly from those of 

 A. petasus. 



The chief difference is in the intermuscular septum, which diminishes rapidly 

 distally instead of being parallel sided as in A. petasus. 



The ridge forming the distal border of the interarticular ligament fossae 

 is not nearly so high and well developed, and the angle which it makes with the 

 transverse ridge is somewhat greater. 



The muscular fossae are proportionately smaller than those of A. petasus, and 

 the ends of the dorsal ligament fossae are much more acute. 



The difference in the shape of the muscular fossae as shown in the figures is 

 merely a matter of individual variation, the muscular fossae being the most variable 

 elements of the joint face. 



As in A. petasus, there is little or no calcareous deposit within the ventral sur- 

 face of the radial pentagon. 



Height of articular face (measured along the im-lination), 1.4 mm.; width, at 

 transverse ridge, 2.2 mm. 



ANTEDON ADKIATICA. 

 Fig. 80, p. 53. 



There appears to be but little difference between the radial articular faces 

 of this species and those of A. mediterranea. The muscular fossae are propor- 

 tionately slightly smaller with the outer distal angles more broadly rounded, and 

 the interarticular ligament fossae are narrower as a consequence of their anterior 

 border making a considerably less angle with the transverse ridge. 



ANTEDON BIFIDA. 

 Figs. 904-096, pi. 4. 



COXII'SOMETRA LOVEXI. 

 Fig. 81, p. 53. 



The dorsal ligament fossa is about three times as broad as high, with the 

 proximal border well rounded. The ligament pit is about as large as the central 

 canal, but is not strongly marked. 



The ends of the transverse ridges are not quite in contact interradially. 

 The interarticular ligament fossae are separated interradially by a narrow, shallow, 

 parallel-sided groove, which becomes narrower or almost closed between the mus- 

 cular fossae. 



The outer edge of the interarticular fossae is straight and makes an angle of 

 about 60 with the transverse ridge. The distal edge is straight and makes an 

 angle of about 45 with the transverse ridge. 



