THE FISSURAL PATTERN. 



501 



TABLE SHOWING FOUR METHODS OF ENUMERATING THE " ARCHED GYRI." 



1364. The Angular Gyrus. This name is applied to a fold of the hemisphere in 

 man and monkeys. By a few writers it has been given also to the caudal portion of what 

 Leuret called the third arched convolution. As indicated below ( 1369), we do not think 

 the homologies of the fissures or folds are sufficiently well determined to warrant the 

 application of this name to the Carnivora. 



1365. The Fissural Pattern. The fissures of the cat, dog and fox can be homolo- 

 gized in most respects, yet they differ to such an extent as to be readily distinguishable. 

 If we could accurately determine the arrangement of fissures which is common to all 

 domestic cats and peculiar to them, we might be able to define the fissural pattern of the 

 species. 



In view of 1he inadequacy of our knowledge, we have thought best to confine the dis- 

 cussion of the fissural pattern to a brief statement of what appear to be the constant and 

 the inconstant fissural characters of Fells domestica. 



1366. Constant Characters. (1) Presence of the following nineteen fissures : anterior, 

 ansata, calloml's, coronalis, cruciata, diagonalis, fimbria, hypocampce, lateralis, marginalis, 

 olfactoria, postica, postrhinalis, poxtsylviana , rhinalis, Syhiana, splenialis, superorbitalis, 

 supersylviana. 



(2) Fissura Sylviana rather short, forming not more than one third nor less than one 

 eighth of an imaginary line coinciding therewith and extending from its ventral end to 

 the dorsal margin of the hemisphere. 



(3) Nine fissures are so placed with reference to the Sylvian as to form three irregular 

 arches dorsad of the Sylvian, corresponding with the more regular arched fissures of the 

 fox and wolf ; the first consists of the postica and the unterior, the diagonalis often being 

 continuous with the latter ; the second, of the postsyhiana and supersylmana ; the third, 

 of the lateralis, with the medilateralis when 'present, the ansata and coronalis. 



(4) Absence of a fissure (F. cctolatcralis of Canidse) between the caudal portions of the 

 lateralis and the supersylvian. 



(5) Disconnection of the dorsal ends of the anterior a.nd postica. 



(6) Independence of the F. olfactoria. 



(7) Independence of the dorsal ends of the anterior, postica, superorUtalis and Syhiana ; 

 of the ventral ends of the hypocampm, caronalis and medilateralis ; of the caudal ends of 

 the splenialis and postradicalis (when present) ; of the lateral end of the crudata ; of the 

 mesal end of the ansata. 



