974 PELECYPODA. [Eualamdlibrnchia. 



Animal (Dall, P. Mai. S., iii, 85). Animal having the siphons 

 naked, slender, closely united to their very tips, the orifices nearly 

 in the same plane and surrounded by small papillae. The mantle has 

 a thickened edge, smooth for the most part, but near the ends of the 

 shell more or less papillose, with rather distant papillae. The mantle 

 is completely open, except in the central portion of the dorsal margin, 

 not even being united where its margins pass around the adductors. 

 The foot is compressed, sharp-edged, pointed, large and muscular, 

 with no obvious byssal groove, and of a lanceolate outline. Its edges 

 are entire. The palpi are large, narrow, long, smooth external! v. 

 plicate internally, adherent near the small circular mouth. They 

 extend beyond the posterior edge of the visceral mass, becoming 

 distally free and twisted at the ends. The body is connected with 

 the siphonal septum by a D -shaped fleshy septum, from which, on 

 each side, a smooth, fleshy, narrow flap, as long as the septum itself, 

 hangs down into the branchial chamber. Outside these flaps, and 

 seated on the lateral borders of the fleshy septum, are the gills. These 

 present some peculiar features, the most obvious of which is that the 

 gills of the two sides are not symmetrical ; and, further, that on one 

 side, and in some cases on both sides, the plicate laminae are discon- 

 tinuous. The ctenidium of the left side is short and small, the outer 

 lamina smaller than the inner, both dwindle to a point and cease 

 before reaching the vertical of the visceral mass, and there is a dis- 

 tinct vacant space with no trace of a pendant lamina between the 

 anterior termination of this part of the ctenidium and the sinus be- 

 tween the posterior parts of the palpi. Further forward, between the 

 upper and lower palpi, a new lamina, corresponding to the inner direct 

 and reflected lamina of the ctenidium, is developed, and attains a 

 respectable size, being wider than the palps and extended forward, 

 diminishing in size nearly to the front edge of the visceral mass. The 

 right ctenidium is nearly always continuous. Its laminae are larger 

 than those of the left side and extend forward, diminishing in size, 

 between the palpi to a point opposite the middle of the visceral mass. 

 The edge of the anterior segment of the inner direct and reflected 

 lamina of the right side is bifurcate, in front of the anterior edge of 

 the posterior segment. The fleshy septum above described com- 

 pletely separates the anal and branchial chambers. The inhalent 

 siphon opens into the latter by a circular opening capable of being 

 closed by a sphincter muscle or arrangement of fibres. On either 

 side, near this opening, is a large, long sensory lamina, situated on 

 the mantle and extending forward, parallel with the thickened mantle- 

 edge, nearly to the posterior edge of the foot, where the latter joins 

 the visceral mass. 



Type in the British Museum. 



Hob. North and South Islands, in about 5 fathoms ; not com- 

 mon. The type was collected by the Rev. R. Taylor. 



Maori. Kuwharu (teste Captain Bollons). 



