GENERA AND SPECIES. 115 



small, immersed. Disk flattened, black. vSpores two- 

 celled, brownish when mature, 8/a X 4.5/x. 



11. Buellia spuria. Thallus of rather large angu- 

 lar squamules, somewhat convex above with dark mar- 

 gin, light to gray. Apothecia of medium size, adnate, 

 only slightly extending above the thallus, irregular in 

 form and size, often covering the entire squamule, mar- 

 gin somewhat elevated. Disk black. Spores two- 

 celled, dark-brown, 15/a X 7/x. 



12. Buellia pulchella. Thallus well developed, con- 

 sisting of gyrate folds, resembling the convolutions of 

 the brain, greenish-yellow. Apothecia medium to 

 large, sessile. Disk convex, black. Spores two-celled, 

 constricted, dark-brown, 14/x X 7/w,. 



10. Catillaria. 



This genus requires further careful study. Tucker- 

 man and others included it in the uncertain group 

 Heterothecium. Its general characters resemble those 

 of Lecidea. The hypothecium is dark-blue to black. 

 Thallus is rudimentary. The algae are no doubt Pleu- 

 rococcus. Spores two-celled, large, colorless. Only 

 one species from the United States has come to my 

 notice. 



1. Catillaria grossa. Thallus thin, papery, smooth, 

 almost shining. Apothecia medium in size. Disk 

 flattened, margin elevated, black. Spores two-celled, 

 colorless, large. 



C. grossa occurs upon bark of ash and perhaps other 

 trees. It is not common, and nothing definite is known 

 concerning its distribution. 



