4 PBOCEEDINGS OF THE NATIONAL. MUSEUM vol.82 



nearly flat and reflected to form a slight appearance of an umbilicus. 

 The fold on the columella, characteristic of the genus, is very small, 

 situated rather high up and within, so that it does not show in a 

 front view. Parietal wall with a thin, transparent callus. 



Type.— The type (U.S.N.M. No. 414169) measures: Length, 

 14.5 mm ; diameter, 7.5 mm ; length of aperture, 10 mm. It and a 

 younger specimen (U.S.N.M, No. 363022) were presented by Mrs. 

 T. S. Oldroyd and were collected by J. W. Pemberton, December 

 26, 1914, in the Santa Cruz River at the outlet of Lake Argentino, 

 Province of Santa Cruz, Argentina. The latitude and longitude 

 quoted on the label are 50° 15' S. and 71° 48' W., respectively. 



Remarks. — This interesting species makes a near approach to be- 

 ing unicolored and upon cursory examination it would be said to 

 be uniform light olive-green, but closer scrutiny shows it to possess 

 the reddish spots and tinges characteristic of the genus. What spots 

 show are arranged in bands and have a marked tendency to assume 

 an arrowhead pattern. The sculpture, though nearly microscopic, 

 is essentially the same as that of C. I'hnnaeformis Dall, type of 

 Dall's subgenus Pseudochilina (U.S.N.M. No. 56423), and were 

 that subgenus valid the species might be placed with it. In the 

 weak, nearly lacking columellar fold it would fall into the sub- 

 genus Acyrogonia Mabille, in which the columellar plait is said 

 to be lacking, but that subgenus is founded upon a character which 

 shows every degree of variation in strength as we turn from species 

 to species. I have never seen a specimen of Ghilina in which the 

 columellar fold was entirely lacking. It may be very weak and nearly 

 hidden by being set high up on the columella and nearly on its 

 inner edge, but careful examination always has shown that it is 

 present and fulfills in all particulars the definition of typical OhUina. 

 The new species here described is a case exactly to the point. G. 

 simplex is related to a number of other species, perhaps the nearest 

 being C. fulgurata oligoptyx Pilsbry. Both are probably descended 

 from the same or nearly related ancestors. It is related also to G. 

 parchappi minor Marshall of Mar del Plata, Argentina, So far 

 as known to the author, all the species of Ghilina which have a very 

 weak fold belong in the Atlantic drainage. The one described by 

 Mabille {G. fusca) and the one by Mabille and Rochebrune {G. 

 nervosa) came from Punta Arenas, Argentina, which is near the half- 

 way point of Magellan Strait and hence can be said to be in neither 

 the Atlantic nor the Pacific drainage, but in both. 



