316 Br. F. R. Cowper Reed — The genus Homalonotus. 



publication, must also be ascribed to it. The well-marked triloba- 

 tion of the body, the narrow and distinctly defined axis, and certain 

 features of the head-shield (see below under Burmeisterella), as well 

 as the oval or semicircular pygidium, mark off this group from the 

 true H. HerscJieli. The pointed pygidium referred by Woodward ^ 

 to S. Chamjjernoivnei on a subsequent occasion seems to belong to 

 Giirich's group Digonus and is certainly in no way related to 

 H. elo7igatus. 



With H. pradoanus we must associate H. Gervillei, De Vern.,^ and 

 R. Barratti, Woodw.,' the latter from Cornwall. The pygidium has 

 a rounded semi-oval sh.ape, a more or less distinct border, but no 

 acuminate extremity. The axis in both the thorax and pygidium is 

 only faintly marked. The head-shield as seen in S. Gervillei, which 

 is the best-known member of the group, has distinctive features (see 

 below under Parahomalonotus). The surface is ornamented with 

 coarse granules and tubercles, but not spines. S. Gervillei was ^mt 

 described from the Devonian of the Bosphorus, but was more fully 

 described and figured by Bayle (op., cit.) from the Calcaire de Nehou, 

 Manche, France. Another allied French species, S. Sansmanni, 

 llouault,* must be included in this group of species. 



Thus, in addition to the H. Serscheli grou^ (which, is the true type 

 of Burmeisteria), we find three other groups, i.e. (1) the S. rhenanus 

 { = Digonus, Giirich) group, and also the more distinctly marked 

 groups of (2) H. elongatus and (3) of H. Gervillei, all developed in 

 Devonian times and sometimes all included by palaeontologists in 

 Btt,rmeisteria. 



7. Calymenella, Bergeron, 1890. 



Bergeron^ established this genus in 1890 with a new species, 

 C. Boisseli, Bergeron, from the Ordovician of Herault, as its type, 

 and he also included in it the species Calymene Bayani, De Trom. et 

 Lebesc.® The characteristics of the genus were given as follows : 

 " Glabelle peu borabee, arrondie en avant, portant trois sillons, dont 

 les deux derniers sont bien visibles; le posterieur s'inflechit en 

 arriere. Lobes peu accuses. Joues fixes larges. Limbe tres 

 developpe en avant de la glabelle et pouvant se terminer, en 

 pointe. Pygidium de Calymene." The facial sutures are believed 

 to cut the lateral margin behind, but it is not clear if they unite in 

 front on the upper surface of the head at the base of the rostrum. 

 It seems, however, that such may possibly have been the case, 

 judging from some of Bergeron's figures, and this would explain the 

 absence of the rostrum from some of the specimens of the middle 

 shield. The free cheeks are unknown. 



As Porapecki'' has remarked, we may probably regard Calymenella 



' Ibid., Vol. IX, p. 157, PL IV, Fig. 3, 1882. 



2 Bayle, Explic. Carte G(5ol. France, iv, pi. ii, figs. 1, 3, 6, 1878. 



^ Woodward, Geol. Mag., Dec. IV, Vol. X, p. 28, woodcut, 1903. 



'' Rouault, Bull. Soc. Geol. France, ser. II, vol. viii, p. 379, woodcut, 18-51. 



■' Bergeron, Bull. Soc. Geol. France, ser. lll, vol. xviii, p. 365, pi. v, figs. 1-7, 

 1890. 



^ De Tromelin & Lebesconte, Bull. Soc. G^ol. France, ser. Ill, vol. iv, 

 p. 599, 1875 ; Bergeron, op. cit., pi. v, figs. 8-13. 



■^ Pompecki, Neues Jahrb. f. Min. Geol., Bd. i. p. 241, 1898. 



