490 Illinois State Laboratory of Natural History. 



above mentioned and differing somewhat in size and distance 

 apart. They are generally single but here and there are 

 grouped in twos, threes, or fours. The number in a transverse 

 row counted singly or as groups is from thirty to fifty on the 

 middle region of the body. A few others may be scattered 

 between the rows or even form a third broken row between the 

 larger papilla?, particularly on a 3. Along the margins large 

 numbers may be aggregated. The large rough papilla? are 

 prominent wart-like elevations of the integuments, some of 

 which measure more than a millimeter in height in living 

 examples. They appear not to contract under ordinary stim- 

 uli, but are sometimes very much less elevated in preserved 

 material. They are generally conical in shape, their summits 

 bearing a ring of from four to twenty smaller sense papilla? 

 arranged around a central larger one. When the number is 

 greater than eight or nine they are likely to form a less regular 

 ring and to extend further down the sides of the wart, while the 

 central one becomes replaced by two or three. A relation 

 between the size of the wart and the number of papilla? in its 

 crown seems to exist. Of the median series (nip) that on a 2 

 is the largest and often bears twice as many sense organs as 

 that on a 1, which is the smallest. The next series counting 

 laterad (mdp) is always represented by a very large wart on 

 a 3, by a much smaller, frequently absent, one on a 1, and 

 on a 2 is replaced by a rathsr prominent but smooth papilla 

 which supports the dorso-median sensilla (md). This cannot 

 be confounded with the rough papilla?. The next important 

 series (dip) is made up of a large one on a 2, a smaller one 

 on a 3, and a very much smaller one or none on a 1. Just 

 external to the large one on a 2 is the dorso-lateral sensilla 

 (dl), which is somewhat elongated transversely and is litttle 

 elevated above the surface. At the margin are two rows 

 so imperfectly developed that they are probably better 

 described as a single irregular row (dmp) sometimes repre- 

 sented by two warts on a single annulus. Warts of smaller 

 size are generally present, but are more irregularly distrib- 

 uted than the fairly constant ones just described. They are 

 most frequent on a\, where one such is likely to be present 



