92 TRANSACTIONS, NATURAL HISTORY SOCIETY OF GLASGOW. 



fine longitudinal flexuous striae, frequently cross-hatched with 

 delicate lines. Type, Sigillaria leioderma, Brongt. Typical 

 form Sigillaria Brcwdii, forma spimdosa, Germar sp. 



Remarks. — The two sections, Rhytidolepis and Favularia, pass 

 into each other, and only in a few species are distinctly separable. 

 In practice, Favularia is seldom mentioned now even as a section 

 of Sigillaria, as all the species originally placed in it fall 

 naturally into the Rhytidolepis Section. It is only the zigzag 

 appearance of the furrows, brought about by the projecting lateral 

 angles of the alternate leaf-scars, which has given rise to the 

 separation of these forms into different sections. 



In the Rhytidolepis Section the leaf-scars are almost always 

 more or less distant, and the ribs frequently enlarge slightly at 

 the part where the leaf-scar is placed, which imparts to the 

 furrow a slightly wavy course. The surface of the ribs is seldom, 

 if ever, entirely free from surface ornamentation, for even in 

 Sigillaria ovata, Sauveur, which is generally supposed to have a 

 smooth bark, when well-preserved specimens are examined with 

 a lens its outer surface is seen to be covered with very short, 

 fine transverse lines. These impart a granular appearance to 

 the surface. A similar condition occurs in other species with 

 "smooth ribs." Such delicate lines are, however, frequently 

 effaced through imperfect preservation. 



The most common form of ornamentation is two rows of short 

 transverse lines or notches, which extend from the base of the 

 leaf-scar, separating as they proceed, till they reach, or nearly 

 reach, the scar below them. 



A short distance above the leaf-scar is frequently a transverse 

 lunate or straight furrow, accompanied by a few faint irregular 

 transverse lines, and immediately above the scar is generally 

 seen a small punctiform cicatricule. 



The leaf- scar in many species rises up towards its lower margin; 

 this is well seen in Sigillaria mamillaris, Brongt. This character 

 was probably more constant than generally supposed, but has 

 been effaced in the majority of cases through pressure. 



The ornamentation of the interfoliar space of the rib varies 

 much in the different species. In Sigillaria scutellata it 

 consists of one irregular band down the centre of the rib, 

 which extends almost to the succeeding leaf-scar, and above 



