656 THAXTER. 



As material has accumulated the difficulties of the genus have 

 become increasingly apparent, and the variability of many forms is 

 such that anyone who did not have access to large series of specimens 

 would undoubtedly have little hesitation in separating specifically 

 many more forms than are recognized in the present treatment. The 

 variability of many forms is remarkable and confusing. The difficulty 

 is further increased by the fact that some of the species are not only 

 widely distributed, but inhabit varied hosts which do not always belong 

 to the same genus or even family, and it is thus quite unsafe to describe 

 isolated forms without a considerable knowledge of the genus and its 

 variations. S. constrictus, for example, is a case in point, being widely 

 distributed and very variable; and, although it is found only on genera 

 of Oscinidae, inhabits very diverse forms in this famil.y. S. Scapto- 

 myzae and S. Limnophorae are also examples of widely distributed 

 and very variable types inhabiting diverse hosts, in different families. 



The character of the appendage is evidently the most reliable means 

 of distinguishing species, but even this may vary in some instances, so 

 that the number and arrangement of the antheridia and androphorous 

 cells is not always a safe guide. 



In preparing the following descriptions I have found it desirable to 

 distinguish the four regions of the perithecium, which correspond to 

 the four successive tiers of wall-cells, as venter, neck, tip and apex, 

 these being more or less clearly differentiated in a majority of species 

 by differences in diameter, the presence of subtending elevations or 

 depressions, superficial granulation, verrucosity and the like. The 

 cells immediately below the perithecium are similar to those the 

 arrangement and nomenclature of which in Laboulbenia were given in 

 my first Monograph: consisting of three 'basal' cells, immediately 

 below the ascigerous cavity or partly surrounding it; an external cell, 

 the secondary stalk-cell; and the primary stalk-cell, corresponding to 

 cell VI in Laboulbenia. « The term receptacle is restricted to the basal 

 and subbasal cell, and the stalk-cell of the appendage is that which lies 

 immediately below the insertion of the appendage and is variously 

 related to the cells about it. 



It may here be mentioned that S. Anoplischii, originally described 

 from Argentina, has again been obtained from Trinidad, B. W. I., and 

 from Mexico, on genera of Elateridae, and that a peculiar form, S. 

 Lasiochili, the first in the genus which has been recorded on a hemip- 

 terous host, is included in the following enumeration. 



