178 



14. The genus Diplacoden is distinguished from related genera : by the 

 triangle of the fore wings long and narrow, free (usually) and followed by two 

 rows of post-triangular cells (three or four rows in related genera); and by the 

 last antenodal not continuous. Diplacodes minusculian could not be traced out by 

 the key to genera, "DragonHies of Indiana," p. 250. The hind lobe of the pro- 

 thorax in this species is narrower than the middle lobe, sides straight, but with 

 the hind margin emarginate, giving it a bilobed character. The supratriangular 

 space is free and there are eight antecubitals in the front wings. In the arrange- 

 ment of the genera in the " Dragonflies of Indiana " i*ip/acode.s may be placed 

 between Fachydiplax and Nannoikemis. Old males of Diplacodes minui<culum, like 

 old males of Nannothemis bella, are entirely pruinose. 



ESKERS AND ESKER LaKES. 

 By Charles R. Dryer. 



(Published in full in .Journal of Geology, Vol. IX, p. 123.) 

 (Abstract.) 



(1) The saud, gravel and till ridges around High Lake, Noble County, 

 Indiana, with their associated lakes and kettleholes, are described and 

 their structure and origin discussed. The till ridge is thought to be a 

 frontal moraine, the others to be the result of subglacial drainage and the 

 sliding or dumping of drift material into crevasses. These forms are so 

 connected in space and related in structure as to render genetic classifica- 

 tion difficult. The system as a whole constitutes an esker-kame-moraine. 



(2) The esker system of Turkey Creek, Noble -County, Indiana, is de- 

 scribed. These sand ridges traverse the valley floor and nearly inclose the 

 basin of Gordy's Lake. High and Gordy's lakes seem to constitute a dis- 

 tinct species for which the name esker lakes is proposed. 



The paper is accompanied by two maps. 



