28 



THE NAUTILUS. 



Meretrix (Eutivela) perplexa Stearns, n. s. 



characters of the shell, 

 by 33 in height and 



Shell waxen-white, porcellaneous, covered vnlh a greenish-yellow 

 epidermis recalling that of Iphigenia brasiliensis or Mactra ponder- 

 osa Jan. The surface under the epidermis is smooth or marked with 

 lines of growth only. The figure sufficiently illustrates tlie other 

 The specimen figured measures 45 mm. long 

 23 in diameter. There is an impressed 

 lanceolate lunule 15 ram. long 

 and about 4'5 mm. in greatest 

 width. As in Tlvela there is a 

 prolongation forward, between 

 the beaks, of the dark epidermal 

 coating of the ligament ; forming 

 a blackish lanceolate area in 

 front of the beaks about 5 mm. 

 long, resembling the dark area 

 Eutivela perplexa Stearns. i^ j{rca. This and the rugose 



subligamentary ridge are reminiscencesof the period when the ances- 

 tors of Tivela had a more archaic type of hinge. There is no 

 defined escutcheon. 



The soft parts in alcohol present several differences when com- 

 pared with Tivela crassatelloides. 



The gills are double, as in that species, but proportionately much 

 larger and broader ; the edges of the mantle are double with a groove 

 between them ; in both species they are open from the sinus to the 

 anterior adductor ; there are no papilhc or granulations in E. Iher- 

 ingi ; tiie foot is elongated, linguiform, and sharp-edged, without 

 sulci or granulations ; the palpi are large and distinctly paired on 

 each side instead of being partially fused ; the siphons are extremely 

 short but rather large, the incurrent with several ranks of rather 

 elongate tentacular processes, the excurrent with a single row of 

 obvious pajjilhe ; the siphons have blackish maculations toward 

 their ends and are joined for most of their length on the adjacent 

 sides. From the dark color of the tissues in alcohol, they were prob- 

 ably reddish or, at least, not white in life. 



On a single shell of many, are two smtill brown maculse, so that 

 the species may sometimes be colored with brown markings. But 

 the differences of proportion and of solidity wliich seem to be very 

 constant, forbid us to unite the present species with E. Iheringi. 



This species was dredged by the U. S. S. Albatross in several 

 places oflfthe mouth of the Rio La Plata in 10-15 fathoms, muddy 

 bottom, associated with Pectxinculus and sundrv XucuUihc. 



