June 7, 1907] 



SCIENCE 



897 



The Crawfishes of the State of Pennsylvania. 



By Arnold E. Ortmann, Ph.D. Memoirs of 



the Carnegie Museum, Vol. II., No. 10. 



There are two groups of animals which 

 seem destined, on account of their abundance, 

 extensive North American range, plasticity 

 and educational utility, to become classics in 

 the literature of American zoology. One of 

 these groups is the Garter Snakes {Tham- 

 nophis) and the other the Crawfishes (Cam- 

 iarus). The importance and utility of these 

 groups does not seem to be generally recog- 

 nized. It is therefore of special importance 

 that Ortmann's recent comprehensive treat- 

 ment of the Pennsylvania species of crawfishes 

 should be generally known. 



In his introduction Ortmann mentions his 

 extensive explorations of the state, in which 

 he traveled over 11,000 miles, and discusses 

 his methods of collecting and finally gives a 

 historical summary of the Pennsylvania 

 species. This section is followed by the taio- 

 nomical and chorological portion of the paper, 

 which includes a key to the species, with de- 

 tailed description of each, full records of th« 

 occurrence of each species in the state and 

 elsewhere, and a critical summary of the 

 geographic range of each species. The de- 

 tailed character of these records makes the 

 work of special value to students of other 

 localities as well as those of Pennsylvania. 



The section devoted to ecology and geo- 

 graphic distribution discusses the subject of 

 habitat preference, geographic origin and dis- 

 tribution, ecological relations (burrows, chim- 

 neys, etc.), and shows that there are three 

 types of habitat preferences: (1) Those fre- 

 quenting the larger rivers; (2) those frequent- 

 ing small streams ; and, (3) those frequenting 

 springs and swamps. The river species are 

 Cambarus limosus, propinquus and ohscurus. 

 These species are not completely restricted to 

 these conditions, but occur also in any large 

 permanent body of water, a habitat rarely 

 found in Pennsylvania. The small or moun- 

 tain-stream species is C. hartoni.'^ This form 



^ In southern Michigan (Ann Arbor) this spe- 

 cies is abundant in small brooks flowing through 

 open meadows and thus illustrates the habitat 

 variability of this species. 



avoids large streams and tends to push up 

 stream into the head-waters, and further shows 

 a preference for cool waters. The spring and 

 swamp or burrowing species are — C. carolinus, 

 monongalensis and diogenes. These species, 

 says Ortmann, are always found at a certain 

 distance from the open water, although often 

 in close proximity to streams, ditches and 

 ponds; but not in them under normal condi- 

 tions. Ground water seems to be a dominant 

 factor in their environment. It may be sug- 

 gested that the amount of oxygen and carbon 

 dioxide in ground waters, as well as a low 

 temperature, may be intimately related to the 

 habitat preference of these species. (This 

 would be an interesting problem for an ex- 

 perimental study.) The haunts of the various 

 species are discussed, including the shape of 

 the burrows and the construction of the chim- 

 neys. The deeper parts furnish winter, and 

 the upper parts summer quarters. The chim- 

 ney is simply the by-product of the burrow. 



The geographic relations of each species are 

 summarized and discussed in detail; not only 

 with regard to origin in the state, but also 

 their general geographic origin and migra- 

 tion routes. The determination of these 

 routes has required a knowledge of the his- 

 tory of the streams or drainage modifications 

 in Pennsylvania and the adjacent regions. 

 The original distribution of limosus seems to 

 have been influenced by canals and mine 

 drainage. This species is of special interest 

 because it belongs to an isolated group both 

 morphologically and geographically. The al- 

 lied species occur in Missouri, Illinois, Ken- 

 tucky, etc., and its most apparent route is 

 through pre-glacial streams in the now 

 glaciated region; while a northward route, 

 from the south along the Coastal Plain is dis- 

 missed as unlikely. Ortmann concludes that 

 limosus is a Tertiary type which was driven 

 south along the Atlantic Coastal Plain, and 

 within the interior, into Indiana and Ken- 

 tucky, while the species was exterminated 

 from the intervening region. It might be 

 suggested that the preservation of this group 

 of species at the extreme northern part of 

 the Coastal Plain on the Atlantic coast, and 

 the upper part of the Missisippi Embayment 



