159 



Spirifer ziczao Roemer var. undecimplicata Roemer em. Sclpin, 

 PI. XXIII., Figs. 25 and 26. 

 1 885. Spirifer Jindecimplicatiis, Clarke : — Die Fauna dc-s Ibergkalkes 



Neues Jahrb., Beil.-Bd., III., p. 394. 

 1900. Spirifer sierjac var. luideciniplicata, Scupin : — Die Spiriferen 



Deutschlands. Palaeontolog. AbhandL,N, F., IV., 71. pi. VI., fig. 8. 

 This variety is rather easily distinguished from the type species, although 

 their separation as distinct species may not be appropriate, as ScuPiN has 

 already remarked. Clarke, who followed Roemek in accepting the specific 

 value of Sp. iindcci7nplicatiis, described it very excellently though quite briefly. 

 According to him it is characterized by 5 (sometimes 6) strong ribs on each 

 side of the sinus. The sinus itself as a rule bears a single fold, or sometimes 

 one more in addition. These ribs are crossed by undulating growth lines, 



- and the surface usually shows fine granulation. 



On the other hand Spirifer ziczac Ls characterized by him in the follow- 

 ing manner. Usually the sinus possesses one fold, but often two or three, 



"which may be more or less irregulaly arranged. There are 10 to 13 radial 

 ribs on either side of the sinus or the median fold. The surface sculpture 

 consists in fine, irregularly zigzag lines that appear to converge in the grooves 



ibetween the radial ribs. These hnes are most conspicuously distinct on the 



- sinus, where the sculpture has a feathered appearance. They are at times 

 interrupted and then look somewhat granulous. 



The difference between these two forms is indeed very conclusive as far 

 as the descriptions above quoted alone are concerned. Scupin's critical study 

 however, concludes that Sp. uiidecimplicntiis is but a variety of Sp. zicrjctc 

 Roemer. The former differs from the latter, Scupin says, only " durch etwas 



igeringere Zahl groberer Rippen sowie durch bedeutendere Grosse." Roemer 



• counted 8- 10 radial ribs on each side of the sinus in Sp. siczac, though 

 Clarke defined the number to be 10-13. It can be reduced to 6, observes 



.'ScuRiN, in the typical species of Sp. ziczac, and this number " iibertrifft die der 

 RoEMER'schen Originalabbildung von Spirifer nndeciinplicatus nur um i und 



'.kann nach der Angabe Clarke's auch beider von ihm aufrecht erhaltenen Art 



