156 REPORT OF NEW JERSEY STATE MUSEUM. 



rather less prominent and no distinct adductor ridge. Terga 

 often rather narrow, occasionally moderately deep longitudinal 

 furrow, and spur often rather long and pointed. Internally 

 articular ridge prominent and crests for tergal depressor muscles 

 well developed or almost absent. Parietes quite solid or often 

 permeated by minute pores, or small irregular square tubes, which 

 only run up each successive zone of growth for very short dis- 

 tances, giving shell cancellated structure, from which corrosion 

 often externally visible. Lengthwise septa, when present, not 

 denticulated at bases. Internal surface of parietes quite smooth or 

 traversed by very slight anastamosing ridg'es, but never by regu- 

 lar lengthwise ribs. Carinal margin of each compartment on in- 

 side projects inwards beyond general surface of shell, and running- 

 downward rests on basal membrane. Lower edge of sheath rarely 

 hollow. Walls lined by purplish or pale brown, sometimes 

 by almost black corium. Numerous tubuli penetrate under 

 sides of walls and opercular valves and intersection of these 

 tubuli give punctured appearance to often corroded surface of 

 shell. Radii usually very narrow, upper and outer edges as 

 seen externally very oblique, rounded and smooth. Sutural 

 edges either quite smooth or sometimes just perceptibly pitted, 

 like basal margin of walls, or occasionally with globular or 

 arborescent little ridges. A\?e very oblique, though sometimes 

 only slightly so, and sutural edges either smooth or obscurely 

 crenated. Basis membranous, minute in pointed specimens. 



Mouth having labrum with teeth each side of central notch un- 

 usually variable, from two each side, four each side, five one 

 side and four on other, five one side and none on other, and 

 six both sides. Mandibles with fourth and fifth teeth small 

 or rudimentary. Maxillae with scarcely even trace of notch 

 under upper pair of spines. First pair of cirri with one ramus 

 one-third or one-fourth longer than other, segments nine and 

 sixteen in two rami. Second and third cirri short, nearly equal 

 in length, with ten and eleven segments. Sixth cirrus with 

 twenty-five segments, each about broad as long, supporting six 

 pairs of spines. Length 2.5 inches. (Darwin. ) 



Remarks. — W^idely distributed in the north Atlantic Ocean. 

 Very common. It lives attached to rocks, shells and wood, 



