16 THK NAUTILUS. 



excavata Fabricius (1779) from Norway (150-300 fms.). Next 

 comes L. goliath from .Japan (775 fms.), which reaches about the 

 same size as excavata. A third form is recorded from the West 

 coast of Patagonia (245-481 fms.), which I shall call L. patagonica, 

 and a fourth L. ayassizii n. sp., from the Gulf of Panama in 322 

 fathoms. A section, Acesta, has been proposed to include these 

 species by H. and A. Adams. 



All of them have fine microscopic radial striae and coarser radial 

 sculpture, which is more pronounced toward the ends of the shell. 

 In all there is a concentric grooving in the channels between the 

 ribs, which, when the channels are narrow, takes on the appearance 

 of punctation. All have a very narrow gape for the byssus and a 

 flattened or impressed lunular area. All have a very general simi- 

 larity externally. The Patagonian species has an astonishing like- 

 ness to L. excavata. It may be useful to record the distinctive 

 characters. 



L. excavata. Convex ; the whole disk radially grooved, the 

 grooving feebler mesially ; the most impressed part of the lunule 

 close to the hinge line, the shell moderately arcuate, the posterior 

 outline roundly convex ; color grayish white ; resilium broad, some- 

 what oblique. Alt. 140 ; lat. 106 ; diam. 55 mm. 



L. goliath. Flatter, broader, the middle of the disk smooth, 

 posterior radials fine and close-set ; most impressed part of the lunule 

 lower down, the lunule itself longer, the shell more arcuate ; color 

 milk white, sometimes with a yellow flush inside, hinge line longer 

 and resilium slightly more central. Alt. 140 ; lat. 106 ; diam. 36 mm. 



L. patagonica. Narrower and less convex, the whole shell 

 straighter vertically, the lunule narrower and less impressed, a 

 slight tendency to divarication in the obsolete radials of the middle 

 of the disk, otherwise like L. excavata. Alt. 100; lat. 72; diam. 

 31 mm. 



L. agcissizii. Moderately convex; the radial grooving quite uni- 

 formly distributed distally, feebler mesially near the beaks, the inter; 

 spaces smoothly convex, and not sharp and corrugated anteriorly; 

 lunule short, deep and narrow, anterior end of the hinge-line very 

 short; area of the hinge narrow, and the resilium and pit very 

 narrow and oblique ; color chalky white, with a yellow periostracum. 

 Alt. 97 ; lat. 78 ; diam. 30 mm. 



L. goliath and L. patagonica show distinctly obsolete lateral teeth 



