ball: mollusca and brachiopoda. 425 



Xylophaga mexicana Dall, n. sp. 



Shell small, short, posterior area rounded behiud, concentrically marked only 

 with iucremeutal lines; median furrow wide, channelled, in the adult bounded 

 behind by a flattened thread, in front the elevated margin of the channel is 

 obliquely serrate by the terminations of the sagittate sculpture of the anterior 

 area, which a little more anteriorly becomes very fine, so as to require strong 

 magnification to bring out its character ; anterior margin of the valves with a 

 rectangular sulcus, from whose apex an impressed line proceeds to the umbo, 

 the angulation of the sculpture resting on this line ; anterior auriculatiou small ; 

 anterior dorsal margin strongly reflected ; interior smooth except for a strong 

 flattish rib which extends from the umbo under the middle of the wider external 

 channel; umbo much incurved ; myophore small and slender. Alt. 4.2 ; Ion. 5.2 ; 

 diam. about 4.0 mm. 



U. S. S. "Albatross," station 3422, off Acapulco, Mexico, in 141 fathoms, 

 mud, bottom temperature 53.5. 



Two right valves were dredged as above. 



JOUANNETIXAE. 



PHOLADIDEA Tlrton. 

 Pholadidea (Penitella) minuscula Dall, n. sp. 



Shell extremely small, white, subequivalve, with rounded, reflected processes 

 behiud, that on tlie right valve slightly more concave and larger; posterior area 

 sculptured only with incremental lines medial, sulcus shallow ; anterior area sculp- 

 tured with doubly arcuate paired elevated lines, more distant near the sulcus and 

 more crowded anteriorly ; these are angulate at a point corresponding to the ante- 

 rior marginal sulcus, and crossed by sharply incised striae which break them up 

 more or less into segments, especially in front ; anterior dorsal margin recurved, 

 with quite a space under the reflection in front of the umbo; mesoplax single, 

 small, elongate; protoplax cordate, small, single; in the adult the callum com- 

 pletely closes the anterior hiatus. Lon. 4.0; alt. 2.5; diam. 2.5 mm. 



Boring in the corky envelop of a large seed, dredged by the U. S. S. "Alba- 

 tross," at station 3392, Gulf of Panama, in 1270 fathoms, hard bottom, tempera- 

 ture 3f)°,4 F. 



Tliat the species is adult is evident, because the anterior hiatus is completely 

 closed by a well-calcified callum. It is perhaps the most minute adult pholad yet 

 reported. 



Teredinidae. 



TEREDO LiNXE. 



? Teredo, sp. indet. 



A tube, belonging to Teredo or Xylotrya, was dredged by the " Albatross," at 

 station 3393, Gulf of Panama, in 1020 fathoms ; but it may have sunk from de- 

 cayed driftwood disintegrating at the surface of the sea. 



