498 



BRITISH GRAPTOLITES. 



Specific Characters of Forms belonging to the Genus Monogeaptus. 



GROUP II. 





M. aiavus. 



3f. Sandergoni. 



Jf. incommodui. 



M. temiii. 



M. argufut. 



Character of polypary . 



Very long and 



slender with 



slight dorsal 



curvature 



Very long, with 



ventral 



curvature 



Irregularly 

 curved 



Slightly arcuate 

 throughout 



Arcuate distally 

 and involute 

 proximally. 



Maximum width . 



1-2 mm. 



•7 mm. 



•6 mm. 



1 mm. 



15 mm. 



Length of sicula . 



2 mm. 



1-6 mm. ? 



— 



— 



— 



Characters of thecae : 

 1. No. in 10 mm. 



9—8 



8—6 



8-7 



7—5 



8 



2. Overlap 



i as maximum 



1 



h-i 



i-i 



h 



3. Apertural margin . 



Slight sigmoid 

 cui-vature, with 

 slight intro- 

 version 



Introverted 



Even and 

 slightly intro- 

 verted 



With abrupt 

 expansion and 

 slight intro- 

 version 



Introverted and 



slightly intro- 



torted. 



4. Proportion length 

 to width 



5 : 1 



15: 1 



15: 1 



5 : 1 



12 : 1 



GROUP III. 





M. vomerirtus. 









M. 

 griesloniensU. 



M. crenularie. 



31. gajaensif. 





var. basilicus. 



var. ffracilis. 



var. crenu- 

 latui. 









Character of polypary . 



Approxi- 

 mately 

 straight 



Broader 



Proximal 



portion 



gracefully 



recurved 



— 



Slightly 



flexed, very 



long and 



slender 



Long, 



arcuate 



throughout 



Straight or 

 with slight 

 curvature 



Maximum width . 



2 mm. 



3 mm. 



1'6 mm. 



— 



•7 mm. 



1 mm. 



2 mm. 



Length of sicula . 



15 mm. 



— 



1'2 mm. 



15 mm. 



•6 mm. 



— 



1 mm. 



Characters of thecae : 

















1. No. in 10 mm. 



11—10 



— 



13 



13-10 



10 



12—10 



10—9 



2. Overlap 



^ 



2 

 3 



— 



— 



\ 



i 



i-* 



3. Apertural margin 



Everted or 

 in excava- 



— 



— 



Apertural 

 excavations 



Excavations 

 relatively 



Slightly 

 everted or in 



Changing 

 from sliglit 





tions 







smaller 



wide 



excavations 



retroversion 



to eversion 



with tag. 



4. Proportion length 

 to width 



3 : 1 



6: 1 



3 : 1 



— 



3 : 1 



6: 1 



4: 1 



