HISTORY OF RESEARCH. xxv 



drawings); (11) Gr. SedgwicJdi; (12) 6V. txidus ; (13) (//•. BccM; (14) Gr. Nilssoni ; 

 (15) Gr. convolutus (?). Under the name (16) Gr. colonus (Barrande) he figures 

 several specimens which probably represent various aspects of Mono, vomerinus 

 (Nicholson). In addition to these forms, which had been already described l)y 

 previous authors, Suess figures two new species in this group, viz. (17) Gr. dubius 

 and (18) Gr. falx. Of these, however, only the first is identifiable at the present 

 day as a distinct species. 



In his Group 2 (Graptolitlnis) Suess describes (19) Gr. tarriculatus ; (20) Gr. 

 protens, and a new form (21) Gr. armatus. 



In his Group 3 (Bastrites) he includes (22) (Jr. LiniuBl ; (23) Gr. far/nx ; 

 (24) Gr. j^eregriuns ; and a new species, (25) Gr. Barrandei. 



jggj In 1851 Richter published a second paper, entitled 



Eichter, " Ueber Thiiringische Graptolithen." This paper is supple- 



"Ueber Thuiingisclie mentary to the one previously published by him in 1850, and 



Graptohtheu," while the views of Barrande as regards the structure of the 



■ ■„, ^ , .'..'' ■ Graptolites are, to a large extent, incorporated in it by Richter, 



G-esell., Bd. HI. '■ , . i-n t i i in 



they are m many particulars amplified by the results and con- 

 clusions drawn from his own researches. 



The paper contains a descriptive list of species obtained by him from the Alum 

 shales of Thiiringia, viz. (1) Gladiolites Geinitzianus ; (2) Dijmon palmeus ; (3) D. 

 ovatus (Avhich he regards as probably only a variety of D. palmeus or I), folium.) ; 

 (4) Gr. priodon ; (5) Gr. colonus ; (6) Gr. Beclci ; (7) Gr. nuntius ; (8) Gr. Halli ; 

 (9) Gr. hohe miens ; (10) Gr. testis ; (11) Gr. chimsera ; (12) Gr. proteus ; (13) Gr. 

 turricidatus ; (14) Bastrites gemmatns ; (15) B. Linnseij (16) B. peregrinus. 



Richter confirms Barrande's views on almost all points of structure, and, in 

 addition, he draws attention (simultaneously with Scharenberg) to the special 

 organ now known as the " sicula " (Lapworth), which he calls the fnss (foot, base, 

 or pedestal). His figures (1 to 3) represent it as being jointed. He regards 

 it as a " prolongation of the axis," generally directed upwards, but occasionally 

 downwards (Biprion folimn). In Gladiolites and Diprion it is always bodkin- 

 shaped ; in Bastrites spindle-shaped. If this organ is actually a " foot," then 

 he considers Barrande's and Suess' view that the thinner end of the polypary 

 is the younger, and the wider part the older, must be erroneous. He believes 

 that the skeleton of the polypary probably possessed little or no rigidity, and 

 therefore that the form of the polypary, except in Gr. turricidatus, was not 

 constant. 



Mode of Occurrence. — Richter draws attention to many interesting facts bearing 

 on the mode of occurrence of the Graptolites. He points out that they always lie 

 on the surface of the rock, and are never found upright or traversing the sliale ; 

 and that they are generally arranged quite irregularly— implying, apparently, that 

 they did not live fixed in the mud where they are now found. According to 



d 



