690 DEEP WATER MOLL USES AND BBACHIOPODS—DALL. voL.xvn. 



ing a band; witbin the margin is a little elevated rednplication of the 

 inner layer, the edge of which appeared to be minutely papillose, and 

 which in life can probably be extended to several times its length as 

 preserved in spirit. In front the lobes are separated in front of the 

 anterior adductor and continue distinct three fourths of the way to 

 the incurrent siphon, Mdien they are joined; around the oval area 

 occupied by the ijapillse about the siphonal orifices the border of the 

 mantle, dividing again, forms a thickened frame whicli is united in 

 front of the posterior adductor. The sides of the mantle in front of 

 the incurrent siphon — below the middle line of the valves (drawn hori- 

 zontally) and on each side of the pedal opening forward to the vertical 

 of the anterior adductor — present rounded-triangular areas with their 

 apices anterior, where the tissue of the nmntle between the inner and 

 outer laminae of each lobe is tliickeued by the presence of a quantity 

 of columnar nuiscular tissue perpendicular to the surfaces of the 

 laminib and very uniformly distributed. Tliese areas are crossed by 

 numerous branches (more or less bifurcated) given out by the pallia! 

 nerve, and the outer face of the area thus modified is attached to the 

 valve, upon which it leaves somewhat vermicular surface markings. 



Several longitudinal or radiating fibers or bands parallel to the 

 surface of the mantle are also observable by transmitted light, the 

 chief of which extend toward the base of the incurrent sijihon or in 

 the direction of the anterior adductor. These masses of muscle have 

 no obvious function; they occupy the area of the radiating retractors 

 of the siphons in ordinary sinnjmlUafa, but they are not connected 

 with the siphonal septum or the sphincter of the incurrent siphon and, 

 with few exceptions, the columnar fibers simply connect the inner and 

 outer lamiuse of the lobe of the mantle in which they are respectively 

 situated. Over the surface of the muscular mass near the median line 

 behind the commissure of the mantle edge is distributed a quantity of 

 glandular tissue which reaches up to and partly around the lower 

 portion of the sphincter of the branchial siphon between the lamiuie of 

 the mantle lobe. The aggregation of glandular cells is so arranged as 

 to leave channels which lead toward the vicinity of the sphincter, 

 where they probably open to the surface, though I was not able to 

 detect the orifices. The internal face of the incurrent siphon is con- 

 centrically wrinkled by the contracted sphincter, which below seems 

 to merge with the pallial marginal band and above is overshadowed 

 by a broad, smooth siphonal septum. The orifice itself, as retracted, 

 from an internal point of view, presented a vertical smooth edged slit, 

 of M'hich the margin projected internally to a marked degree. Exter- 

 nally the perisiphonal area is papillose, the papillae not seemingly 

 arranged in regular ranks, but the outer ones larger and the size dimin- 

 ishing focally toward each orifice. One papilla, larger than any of the 

 rest, is situated in the median line above the excurrent orifice, but there 

 is no medial papilla ventrally. The excurrent siphon, as usual, is 



