178 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 109 



5 (from 8.5 to 13 mm.) on Sept. 22, 1949. Three were taken in a 

 plankton net when it touched bottom: 1 (4 mm.) on Nov. 1, 1949, 

 and 2 (2.5 and 3.8 mm.) on July 13, 1950. Eleven (from 3.1 to 5.5 

 mm. long) were dredged at a depth of 10 feet on Oct. 11, 1949; 1 

 (17.4 mm.) at 72 feet; 2 (18.9 and 24.6 mm.) at 80 feet on Aug. 21, 

 1948; 1 (9.5 mm.) at 132 feet; 1 (20.3 mm.) at 175 feet; 6 (from 16 

 to 27 mm.) at 246 feet; 2 (17.6 and 20.6 mm.) at 295 feet; 3 (5.6, 

 15.1, and 15.2 mm.) at 341 feet; 3 (2.5, 12.2, and 15.3 mm.) at 453 

 feet; 1 (19 mm.) at 522 feet; and 2 (11 and 13.7 mm.) at 741 feet. 



In all of the Point Barrow specimens the umbos are eroded — even 

 the very smallest ones are somewhat eroded. Two of the specimens 

 that washed ashore on September 22 contained very large eggs and 

 another contained eggs in earher stages of development. 



Other material examined. — The types of L. viridis, L. becki, L. 

 aniwana, L. scammoni, and L. schefferi (there is only one specimen 

 of L. schefferi) and all other specimens of these species as well as all 

 of the specimens of i. Jluciuosa in the U. S. National Museum. 



Discussion: After examining these specimens and taking many 

 measurements, I am of the opinion that the above species are but 

 variants of L. fluctuosa. Arctic shells are highly variable, and the 

 variations exhibited by these "species" are no greater than, perhaps 

 not so great as, those found in Astarte borealis and A. montagui, for 

 instance. Young specimens of Liocyma fluctuosa tend to be more 

 trigonal than larger specimens. Specimens of L. viridis are no more 

 produced and arched along the ventral margin than many specimens 

 of L. fluctuosa; in some specimens of L. viridis the sinus is rounded 

 and in others it may be sharply angulated, and these same variations 

 may be found in the sinus of L. fluctuosa; muscular scars are no 

 smaller than those in comparable specimens of L. fluctuosa. L. schej- 

 jeri is a tumid specimen in which the concentric sculpture is faint 

 except at rather evenly spaced intervals, where flattened waves occur. 

 Similar sculpture may be found in specimens of L. viridis, L. becki, 

 and L. fluctuosa (pi. 23, fig. 8). Still other specimens of these last 

 three forms may have closely spaced concentric undulations in various 

 combinations with the widely spaced type. Young specimens of L. 

 aniwana have practically the same proportions as young L. fluctuosa, 

 but the specimen that was selected as the type is especially thin and 

 shallow. 



With the exception of those of L. becki, the percentages given in 

 table 5 fall within the normal limits of variation. It is possible that 

 the specimen selected was an extreme variant rather than typical. 



