no. 1 136. OBSER VA TIONS ON THE ASTA GIDM— FAXON. 647 



CAMBARUS PELLUCIDUS (Tellkampf). 



This species lias been found by Mr. W. P. Hay in Shiloh Cave, 

 Down's Cave, and other caves near Bedford, Lawrence County, Indiana, 

 and in a small cave near Paoli, Orange County, Indiana. 1 The speci- 

 mens from these caves belong rather to the form described by Cope as 

 G. inermis (Wyandotte Cave) than to the typical form commonly found 

 in the Mammoth Cave of Kentucky. Mr. Hay has shown that these 

 specimens are very variable as regards the development of the spines 

 of the rostrum and sides of the carapace, and that the reduction of the 

 spines is most marked in specimens from the more northerly localities. 

 A transition is thus formed through these individuals to the following 

 subspecies : 



CAMBARUS PELLUCIDUS TESTII Hay. 



Catiibaru8 pellucidus testii Hay, Proc. U. S. Nat. Mus., XVI, 1893, p. 285, pis. 

 xliy, xxv, figs. 2, 5, 6, 10, 11, 12; Crawfishes of the State of Indiana, 

 p. 484, fig. 4, 1896. 



In this form, which has been found in Mayfield's Cave and Truett's 

 Cave, near Bloomington, Indiana (the most northern locality in which 

 cave crayfishes were found by Mr. Hay), the reduction of the spines is 

 carried to the extreme. The lateral spines of the rostrum, the anterior 

 spines of the postorbital ridges, and the spines on the sides of the 

 carapace are altogether wanting, while the external spine of the second 

 antennal segment and tbe apical spine of the antennal scale are much 

 reduced in length. So this form comes to bear a close likeness to 

 G. bartonii and suggests the possible derivation of C. pellucidus from 

 G. bartonii. It is true that in regard to the structure of the male exter- 

 nal organs G. pellucidus is similar to those species of Gambarus that are 

 placed in Group I. But, as I pointed out in my "Bevision of the Asta- 

 cidte" (p. 18), this type of the male organ is a very simple and primitive 

 one, and might be acquired through an inherent reversionary tendency 

 by cave-dwelling species of any of the groups into which the genus 

 Gambarus has been divided. The presence of hooks upon the fourth 

 pair of legs may, in this case, be correlated with the reversion of the 

 male appendages to the type of Group I. It will be observed that in 

 Form II (the less perfect form of the male) the hooks on the fourth pair 

 of legs are more or less abortive not only in C. p. testii but also in the 

 typical form of G. pellucidus from the Mammoth Cave. 



The difference, pointed out by Hay, between G.p. testii and C. pellu- 

 cidus from Shiloh and Wyandotte caves, with regard to the shape of 

 the hooks on the third pair of legs, probably results from comparing 

 the second form of G. p. testii with the first form of G. pellucidus. 



Three types (two males, Form II, one female) of this subspecies are 

 in the collection of the United States National Museum (So. 17702, 

 Mayfield's Cave, Indiana, W. P. Hay). 



iProc. U. S. Nat. Mus., XVI, 1893, pp. 283- 



