THAXTER. — ARGKNTINE LABOITLBENIALES. 207 



best distinguished by the short coherent primary appendages, short 

 branches, and numerous paired antheridia. 



Laboulbenia Heteroceratis nov. sp. 



Uniformly pale straw-yellow, very variable in form. Jleceptacle 

 usually rather elongate, but sometimes short and stout, the subbasal 

 cells larger than the basal, cells IV and V subequal. Insertion-cell 

 concolorous with the cells below it, the primary' outer appendage 

 short, simple, cylindrical, hyaline, becoming distally flaccid; the 

 inner consisting of a few ill defined short flaccid l)ranches; the in- 

 sertion-cell becoming very variably modified by secondary divisions, 

 w'hich may also involve the basal cells of the appendages so that the 

 primary outer appendage may even become completely surrounded by 

 small cells bearing either branches or cur^•ed antheridia, the branches 

 sometimes forming a tuft of some length. Perithecium asymmetrical, 

 the inner margin usually straight or slightly concave, the outer 

 strongly convex; tapering to a snout-like tip so turned (in the Argen- 

 tine material) that it is viewed sidewise and shows a blunt symmetri- 

 cally rounded apex, subtended by a purplish shade. Perithecium 

 110-120X35^0 At. Receptacle 156-235 ix. Appendages 50-60 m- 

 Total length to tip of perithecium 220-340 /x. 



Growing in various positions on species of Hetcroccros sent from 

 La Plata by P. Spegazzini in 1907, Nos. 1679-80. Also found on 

 species of Heteroceros sent from Kansas by Dr. A. Stewart. 



This very peculiar form varies greatly in general habit, and from 

 the secondary divisions of its insertion-cell and the basal cells of its 

 appendages may assume an appearance very similar to that of some 

 of the aquatic forms on Gyrinidae. Its relationships seem to be 

 e\idently with the forms found on Clivina and its allies; although a 

 similar production of sessile antheridia from proliferous cells such as 

 occurs in the present instance is not seen in other forms. The above 

 description is based in part on material obtained from American 

 species of Hetcroccros which were found among a small collection of 

 beetles kindly procured for me by Mr. Alban Stewart in Kansas City. 

 The measurements given above are from the Argentine material. 

 The Kansas specimens show the slightly oblique asymmetrical tip 

 of the perithecium from the usual point of view. 



