xxxii BRITISH GRAPTOLITES. 



regards the narrow end as the " beginning of the animal," the apertures of the cell 

 thus opening upwards, " facing the light." Some forms, such as Monograpsus and 

 Nereograpsus, he holds to be free-swimming ; while others, like Diplograpsus and 

 ( 'ladograpsus, were probably attached to the mud by their narrow end. 



Affinities. — He adopts the generally accepted view as to the Sertularian 

 affinities of the Graptolites, and disagrees with Boeck's views that they may be 

 part of a larger animal, and therefore not complete in themselves. Geinitz 

 attributes some of the various aspects under which the species present themselves 

 to their flexibility and contractibility, and considers that Pr. teretiusculus possessed 

 a greater elasticity and contractibility than any other known form. 



Classification.. — The classificatory part of Geinitz's work is perhaps the most 

 valuable. He recognises five genera : 



1. Diplograpsus (Diprion and Petalolithus). Geinitz holds that Barrande's 

 name Dvprion, being already in use for an insect, must be dropped, and as 

 Petalolitlius is identical with Diprion, that must be abandoned also. Further, 

 M'Coy's name of Diplograpsus, having the priority, should be adopted for the 

 genus. 



2. Nereograpsus (two-rowed Graptolites without or with a very slender axis). 

 Geinitz emphatically states that these forms are not worm-markings, and that he 

 has been able to recognise the openings of the polyp cells. Geinitz's views of 

 these forms have, however, not been admitted by other palasontologists. 



3. Cladograpsus (" two-armed or forked Graptolites "). Under this name 

 Geinitz includes those species which are now grouped in the genera Dicellograptus 

 (Hopkinson) and Dicranograptus (Hall). 



4. Monograpsus (single-rowed Graptolites with solid axis). This name was 

 proposed by Geinitz to include both the Monoprion and Bastrites of Barrande, and 

 was suggested so as to be analogous to the Diplograpsus of M'Coy. It has since 

 been universally adopted. 



5. Betiolites (double-rowed Graptolites, which are covered on their surface by 

 a net-like skin, and possess a superficial central axis). 



Geinitz points out that the name Graptolithus, or Graptolitlies, can no longer 

 be used for any single division of the Graptolites, any more than the family names 

 Trilobite or Ammonite for a single genus of either of these families. 



Description of Species. — The following species were described and figured by 

 Geinitz, for the most part with great accuracy :— (1) Diplograpsus ovatus ; (2) 

 D. folium ; (3) IK palmeus (some of the figures represent G. rectangularis) ; (4) 

 l>. pristis, His. (which he believes to be identical with Pr. scalaris, His.); (5) 

 D. dentatus (?) (fig. 25 undoubtedly represents the genus now known as Dimorpho- 

 graptus, Lapworth) ; (G) D. bicornis(?) ; (7) D. rectangularis (?) ; (8) D. bullatus (?) 

 (these three last forms Geinitz does not regard as true species); (9) D.foliaceus; 

 (1<») I), cometa (a new form subsequently chosen as the type of the sub-genus 



