NO. 1101. 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



29 



observed in 1819 at Engineer Oantonmeiit, which station was located 

 near the present town of Blair, ISTebraska. This locality, however, is not 

 quite so far Avest as Everett (Dodge County), from which place a speci- 

 men was obtained for the collection of the Department of Agriculture. 



GEOGRAPHICAL VARIATION IN SIZE AND COLOR. 



The common mole varies correlatively with its geographical distri- 

 bution, both in point of size and in color. Generally speaking, the 

 largest individuals are found in the northwestern i^art of its range — that 

 is, in the States bordering on the Great Lakes and the northern portion 

 of the Mississippi Valley generally. The smallest individuals are from 

 Florida and the Gulf coast of Texas. East of the Alleghanies there 

 is a very uniform diminution in size from north to south, and there is a 

 similar but less gradual diminution in the portion of the range west 

 of the Alleghanies, 



The diminution on the Atlantic Coast is well brought out by a com- 

 parison of measurements of the total length of adult skulls, as shown 

 in the following table: 



Average dimensions of adult skulls of Scalops aqiiaticus from different localities on the 



Atlantic Coast. 



Locality. 



Conriecticut 



New York and New Jersey 



Pennsylvania 



Maryland and District of Columbia 



Virginia 



Nortli Carolina , 



Florida ■■ 



Average 



total 

 length. 



mm. 

 35.5 

 35.3 

 34.9 

 34.1 

 33.4 

 31.8 

 30.8 



Number of 

 skulls. 



The Florida specimens, representing the minimum as regards size 

 on the Atlantic Coast, constitute the subspecies australis of Chapman. 

 This form has some other characteristics, of course, besides small size, 

 as will be found upon examining the diagnosis already given (p. 20), 



On the Gulf coast about the mouth of the Mississippi and farther 

 westward in the same latitudes in Texas and thence southward, the size 

 is still very small, though somewhat larger than on the Atlantic Coast. 

 The skulls of fourteen specimens from points about iSTew Orleans, 

 Louisiana, and thence westward to San Antonio and Mason, Texas, 

 have an average total length of 32 mm. Included here is the form 

 known as S. texanus, from Aransas County, Texas, which is practically 

 of the same size as the Florida aS'. australis. 



Seven adult skulls from Itockport, in this county, have an average 

 total length of 30.9 mm. If we include skulls from other neighboring 

 parts of the Texas coast (Corpus Christi, Padre Island, etc.), the aver- 

 age rises to 31.2 mm. 



Uj)on j)assing northward from the Gulf, an increase in size above 



