Descrittioxs of Devonian Fossils. 22 



^H 



In small specinieiis tliis species somewhat resembles the aS'. erratica, 

 but it is more distinctly alternating in structure, has smaller and more 

 numerous vertical columns, and wider interspaces ; it also differs in 

 mode of growth. 



Formation and locality. In beds of white limestone, bordering 

 Lime creek, above Kockford, Iowa ; of the age of the Chemung group. 



SxROMATOrORA (C^NOSTROMA) INCRUSTAN8 n. Sp. 

 Plate 9, flg. 3. 



Parasitic, incrusting other bodies, especially discs of ALVEOLrrEs, 

 sometimes coating them to a depth of three-fourths of an inch. Surface 

 covered with irregularly disposed, conical pustules, distant from each 

 other from one-fourth to five-eighths of an inch ; when perfect, termi- 

 nating at the apex in a minute, rounded perforation, from which pro- 

 ceed several (generally five) flexuous, bifurcating channels, which pass 

 down the sides of the pustules and over the surface of the mass between 

 them, often extending a distance of more than half an inch. In a sec- 

 tion, the older channels are seen beneath the surface, traversing the 

 substance of the mass as round pores, and terminating in the vertical 

 tube of the cell. The pustules are from one-twelfth to one-eighth of 

 an inch at base, and about half as high as the width ; the spaces 

 between strongly granulose. 



In a vertical section, the horizontal layers are so compact and closely 

 arranged as to be counted with difficulty ; while the vertical columns, 

 representing those of true Steomatopora, are mostly obsolete or blended 

 with the transverse plates. 



Formation and locality. In rocks of the age of the Chemung group ; 

 Rockford and Hackberry, Iowa. 



Stromatopora (C^xostroma) solidula n. sp. 



Plate 9, flg. 4. 



Specimens in irregular masses, or incrusting foreign substances, the 

 form of which they frequently retain. Surface extremely irregular and 

 more or less thickly covered with small conical or rounded irregularly 

 disposed pustules, giving origin to minute, indistinct, flexuous, rami- 

 fying channels, which traverse their sides and the intervening spaces, 

 seldom extending to any great distance. Vertical section showing 

 closely arranged horizontal layers of varying density, giving a strongly 

 lamellose appearance : the individual plates or vertical columns scarcely 

 or not at all distinguishable, but showing the ramifying tubes of differ- 

 ent sizes very distinctly. 



This species may be easily distinguished from any of the foregoing 

 by the great density and compactness of the substance. 



Formation and locality. In marly beds of the age of the Chemung 

 group ; Hackberry, eight miles above Eockford, Iowa. 



