THE NAUTILUS. 1 1 7 



G.japonica called patruelis or tabuensis by some authors, but which 

 is probably not really that species. The much depressed form like 

 a thick lens, the open umbilicus and want of spiral strife are its more 

 prominent features. It is named in honor of FRIEDRICH WIEG- 

 MANN, of Jena, author of numerous and valuable works on the 

 anatomy of land snails. 



A NEW LYKOPECTEN. 



BY W. H. BALL. 1 



The group of Pectinidae named by Conrad Lyropecten, of which 

 P. Heermanni Conrad is the type, is known to have its precursors in 

 the OHgocene, to be in its developed form characteristic of the 

 Miocene of the Northern Hemisphere on both sides of the Atlantic, 

 and to be represented in succeeding horizons only by degenerate 

 types which can hardly be referred to the same section of the genus, 

 though apparently descended from it. 



The Pacific coast species hitherto known are P. Heermanni Con- 

 rad, 1855 (+ P. estrellanum Conrad, 1856, not 1857); P. magnolia 

 Conrad, 1857 (+ P. crassicardo Conrad, 1862). The first men- 

 tioned is a species of moderate size with no analogue in the Atlantic 

 Miocene; its exact horizon is still doubtful. The second, which cor- 

 responds in the West American fauna to P. Jeffersonins Say is 

 found in the upper or San Pablo horizon of California. From the 

 still newer (?) horizon of Rio Dell on the Eel River, California, Mr. 

 J. S. Diller of the U. S. Geological Survey has obtained a new form 

 of which this preliminary notice is given, not only as a new species 

 of interest but as one of the largest species of Pecten yet known. It 

 will be illustrated later in the Survey publications. It is the ana- 

 logue of P. Madisonius Say. 

 Pecten (Lyropecten) Dilleri n. sp. 



Shell large, rather compressed, nearly orbicular with a relatively 

 short, straight hinge-line, dorsally rectangular, nearly smooth, sub- 

 equal ears, the posterior with three .small riblets ; a well marked 

 though shallow byssal fold ; and moderately thick valves. The 

 right valve is somewhat more convex and strongly sculptured, bear- 



1 By permission of the Director of the U. S. Geological Survey. 



