50 ILLINOIS BIOLOGICAL MONOGRAPHS {148 
In the largest specimen of this species, from the Sangamon River, the 
right valve has a large blister parallel with the postero-ventral border, 
measuring 17 by 7 mm., and anterior to this blister a group of twenty of 
more ‘pin-head’ pearls. There are several of these small pearls in the center 
of the valve. The left valve has a number of ‘pin-head’ pearls bordering the 
pallial line and one larger (1 mm.) black pearl in the center of the valve. 
(Z11230 A). These may have been caused by distomid parasites, although 
none were observed in the animals of this species. Only one shell in a dozen 
were thus affected. 
28. Carunculina parva (Barnes). 
This diminutive mussel is characteristic of the smaller tributaries of 
the Big Vermilion River. It occurs commonly in the ditch above Urbana 
and also in Spoon River. No living specimens were found between the 
Spoon River tributary and the station one mile above iron bridge north of 
Sidney, a distance of over six miles. From this station to the railroad 
bridge east of Sidney, a distance of three miles, this species was abundant 
or common. It is infrequent at Homer Park and was not found in the 
Salt Fork below Muncie or in Middle Fork. Its normal habitat in the Salt 
Fork is on a mud bottom in quiet water. At Homer Park, however, it 
occurs sparingly on a gravel bottom in very shallow water. 
The species as found in Salt Fork is normal in form but not of large 
size, the largest specimen observed, from the railroad bridge east of Sidney, 
measuring 30 mm. in length and 18 mm. in height (Z11096). The surface 
in the Salt Fork specimens is rayless, the color being brown from the um- 
bones to the center of the valve, the balance of the shell being black. 
Specimens from Spoon River were smaller than those from farther down 
the stream. 
Parva occurs infrequently in the Sangamon River at Mahomet on a 
mud or sand bottom. 
29. Carunculina glans (Lea). 
This small mussel, which is much higher in proportion to its length 
than parva, is very rare in Salt Fork, where it was found at but three 
stations, living individuals being collected only below the dam at Homer 
Park. Like parva, it is a species of the smaller tributaries and its normal 
habitat is on a mud bottom. It was not found in the Sangamon River at 
any station examined. 
Frierson (1914: 7) has identified Lea’s glans with the shell called 
Unio (Toxolasma) lividus of Rafinesque, changing the generic, name, 
accordingly, to Toxolasma Rafinesque. In this he is followed by Ortmann 
(1918:572, 573). Should these names be plainly identifiable from the 
original descriptions, these small shells will bear the names Toxolasma 
parvum (Barnes) and T. lividum Rafinesque. The writer wonders whether 
