io8 



The capitulum is elongate, twice as long as broad, rather flat. Its occludent margin 

 is nearly straight, its carinal inargin strongly arched. The apex of the tergum is pointed. The 

 surface of the valves is here and there, especially at the occludent side, covered with membrane, 

 bearing short hairs. There is a distinct chitinous interspace between the carina and the other 

 valves. The valves of the lower whorl are strongly developed ; the upper margin of the carinal 

 latus is the prolongation of the same margin of the rostral latus. 



The scutum is quadrilateral, about twice as long as broad. Its lateral and occludent 

 margins are parallel and nearly straight. Where the occludent and tergal margins meet the 

 slightly pointed and recurved ape.x projects over the tergum. 



The tergum is triangular, with the scutal margin straight, the occludent margin also 

 straight, the carinal margin slightly convex in the lower part, nearly straight in the upper. The 

 apex pointed, but hardly produced. 



The carina is strongly bowed, with the umbo at the apex. It has a flat roof bordered 

 by ridges and increasing in width, but not very considerably, from the apex downwards. The 

 sides of the carina are flat; their width in the middle is slightly less than near the upper and 

 under extremity. 



The upper latus is trapeziform ; its tergal and basal margins are of equal length, 

 its scutal margin is twice as long as its carinal margin. The umbo is at the apex which very 

 slightly projects over the scutum. 



The rostrum is hardly visible; as the rostral margins of the rostral latera do not 

 touch one another and as an extremely narrow streak of probably calcareous matter is seen 

 longitudinally in the middle of this interspace, there is reason to consider this as representing 

 the rostrum. 



The rostral latus is quadrilateral and rather high. Its rostral and lateral margins 

 are convex, its upper margin hollowed out, its basal margin short and straight. 



The infra- median latus is triangular, narrow, with the umbo at the apex. It is 

 considerably less in height than the other latera, .so that the lateral margins of the rostral and 

 carinal latus meet above the apex of the infra-median latus. 



The carinal latus is elongate, trapeziform. Its carinal margin is the longest. It is 

 slightly hollowed out in the upper half where the' carina rests against it, and .straight below 

 the umbo. Its lateral and upper margins are of equal length and straight; its basal margin is 

 the shortest. 



All the valves, the carina excepted, are beautifully and delicately striated. 



The peduncle is cylindrical and short. It is covered by well-developed scales which 

 overlap each other like the tiles of a roof. 



Size. The length of the whole animal is 20,5 mm., that of the capitulum 15,5 mm. 



The animal is attached to a long tube in the form of a spiral, the dwelling-place probably 

 of a tubicolous annelid. 



The specimen was collected by H. M. .S. ".Siboga" at: 



Stat. 20S. September 22, 1S99. Lat. 5^39' S., Long. 122° 12' E. Depth 1S86 m. Bottom: solid 

 green mud. 



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