or ARTS AND SCIENCES. 261 



cupular ; disk at length rugulose and tuberculate, blackish within. JFr. 

 Lichenogr. p. 342. — a. terrestris, Fr. — /?. saxatilis, Fr. — /, ligni- 

 aria, Fr. ! Lichen dubius, E. Bot. t. 2347 (e Fr.). L. dubia, Turn. 

 ^ Borr. in Hook. Br. Fl. 2, p. 176. Tuckerm. Lich. N. E. I. c. 

 On old rails (/), common ; New England. 



Tribe III. GRAPHIDACEtE, Fr, 



XVII. UMBILICARIA, HofFm. 



, Apothecia superficial ; an originally closed thalline exciple convert- 

 ed into a carbonaceous proper exciple, becoming more or less open, of 

 various form. Disk horny, ascigerous, at length chinky, or gyrose-pli- 

 cate, with an incurved margin. Thallus horizontal, cartilagineous, fo- 

 liaceous, somewhat monophyllous, affixed by a central point. 



This most natural genus can, perhaps, still be retained in the place 

 given it in the Lichenogr aphia EuropcBa, though I have, in pursuance 

 of Fries's suggestion (1. c. p. 347), confirmed by all the observations 

 that I have been able to make, preferred to alter the generic character, 

 and make it indicate more fully the relations of the group. It appears 

 to me as analogous to Biatora as to Sticta ; and as the former genus is 

 considered to indicate a Lecideaceous type, irrespective of its approxi- 

 mations to Parmelia, so Umbilicaria may perhaps be taken as typically 

 representative of a peculiar (perhaps properly lirellseform, or Graphi- 

 daceous) type, irrespective of the approach which some of the species 

 make to the characters of Parmeliacese. 



Sect. I. PATELLATiE. Apothccia orbiculate-patellseform ; disk at length 

 chinky, plicate, or proliferous-papillate. 



1. U. mammulata, Ach. (sub Gyroph.). Thallus membranaceous, 

 smooth, irregularly round-lobed and somewhat crenate, fuscous-nigres- 

 cent ; on the under side very black, papillose-granulate, and fibrillose ; 

 apothecia elevated, orbiculate ; margin rather thick; disk plane, chinky, 

 becoming at length convex, and proliferous-papillate. Gyrophora mam- 

 mulata, Ach. Syn. p. 67. G. mamillata, Muhl. Catal. p. 105. 



Rocks. Pennsylvania, Muhl. (North Carolina, Mr. Curtis !) Very 

 distinct from the next. 



