102 UNITED STATES NATIONAL MUSEUM BULLETIN 29 6 



The mantle possesses the typical teeth with one to three points 

 scattered about the surface, especially the ventroposterior area. Ven- 

 trally pointing heavier teeth are aligned along the ventral side of the 

 lateral bars, and face anteriorly ("upward" in the burrow) just below 

 the aperture in a circle around the mantle. 



The lateral bars are typical. They appear to be rolled thickly on 

 the dorsal edge, and possess extremely small granulations scattered 

 about along their length. The left lateral bar (illustrated in fig. 26a) 

 terminates in an area of a circle of three teeth rather less developed 

 than other specimens of the same genus. The right lateral bar does 

 not possess this terminal cluster of teeth. An auxiliary internal 

 strengthening bar appears in the dorsal curve of the neck area of 

 the mantle. 



The mantle aperture is armed characteristically with two pairs of 

 bifid or haired spines of appreciable length. In addition, series of short- 

 er teeth with fine serrations border the aperture, and a rostrum-like 

 projection appears dorsally from the aperture. The typical comb collar 

 on an inwardly tucked membrane lines the ventral end of the aperture. 

 Stubbings (1961) points »out the effect of maturity in differentiating 

 this apertural armament. The spines can be late in developing. No 

 orificial knob is present. The female appears to be cemented to the 

 burrow in the general dorsal mantle area. 



The mouthparts are typical for the genus. A long labrum extends 

 into the apertural area. Light-weight mandibles each have two finely 

 pointed teeth and many extremely thin hyaline teeth along the cutting 

 edge. A few bristles are present behind this cutting edge, especially on 

 the posterior surface. Mandibular palps with long, soft bristles are 

 present lying along the outer edges of the labrum. The two pairs of 

 maxillae are typical and are not illustrated separately. 



The mouth cirri are very reduced. They are represented by small, 

 unsegmented papillae topped by. two or three hair-like bristles. There 

 are three pairs of biramous, multisegmented terminal cirri, on two- 

 segmented protopods. There is no caudal appendage. The protopods 

 are short, devoid of setae, and divided by slanting sutures. The cirral 

 segment count is as follows : 



Terminal 



cimis: 12 3 



Ramus: anterior posterior anterior posterior anterior posterior 



Right side: 14 18 22 24? 25? 25 



Leftside: 15 20 23 24 24 23 



The setation of the cirral segments is typical, with two pairs of 

 slightly feathery setae of equal length (twice the segment length) on 



