Dr.F. R. Coivper Reed — IVte genus Honnalonotus. 317 



as a subgenus of Homalonotus, but it is at any rate an early and 

 aberrant form. Apart from the presence of the rostrum, it seems 

 allied to the Gres de May species of this genus, rather than to any 

 species of Calymene. A rostrum is developed in more than one genns, 

 and Ampyx and ProboUmn are instances. Vogdes ' would apparently 

 refer his species Calymene rostrata, from the Clinton Formation, to 

 this group or genus Cahjmenella, but it has a typically lobed glabella 

 like Calymene^ and the facial sutures cut the anterior margin on each 

 side of the base of tlie rostrum, which is a triangular projection of 

 the border, and therefore is structurally distinct. 



<S. Bigmms, Giirich, 1909. 



The type-species chosen by Giirich is H. gigas, Iloemer,* and 

 Giirich's ^ definition of the subgenus may be rendered as follows : 

 Middle-shield truncate or concave anteriorly, so that the front 

 margin is biangulated; glabella subquadrate ; pygidium with 

 pointed extremity. The section is characteristic of the Lower 

 Devonian, and includes a large number of Continental species, of 

 Avhich Giirich mentions S. scalrosiis, Koch,* and II. rJienamis, Koch.^ 

 "VVe may add to Giirich's definition the fact of the distinct segmenta- 

 tion of the pygidium, which separates these European Lower 

 Devonian species from Bipleura, as Kayser pointed out in a footnote 

 to Koch's memoir (op. cit., p. 10). Perhaps the British species 

 H. go7iiopygceus, Woodw.,'' belongs to this group, as the pygidium, 

 which alone is known, agrees with Giirich's type in general 

 characters. 



The truncate straight or concave anterior end of the middle- 

 shield in the type-forms corresponds to tlie course of the transverse 

 commissure of the facial sutures, and the peculiar course of this 

 commissure seems to mark of$ this group of species from the 

 II. Herscheli group, which they resemble as far as the_ pygidium is 

 concerned. In none of them is the true anterior margin of the head- 

 shield known, so that we are ignorant if the epistome projects in 

 front or if there is a wide pre-sutural area. For these reasons they 

 may be regarded as distinct from the typical Barmeisteria group, and 

 they seem worthy of complete separation from it. 



9. Schizopyge, Clarke, 1913. 



Clarke^ suggested this name for the aberrant species S. longi- 

 caiidatus, d'Archiac, Fischer, and de Verneuil,® of the Lower 

 Devonian of Constantinople, and the two Brazilian species, 



^ Vogdes, Amer. Journ. Sci., ser. in, vol. xxiii, p. 475, 1879; id., Proc. 

 Acad. Nat. Sci. Philad., 1880, p. 176, figs. 1, 2; id., Bibliogr. Palseoz. Crust. 

 (Occas. Papers Calif. Acad. Sci., iv, 1893, p. 223). 



- Eoemer, Verstein. Harzgeb., t. xi, p. 39, fig. 10, 1843. 



" Giirich, Leitfossilien, Lief, ii, Devon, pp. 156, 157, fig. 42, 1909. 



* Koch, op. cit., p. 115, pi. iii, figs. 8-10 ; pi. iv. 



■^ Koch, op. cit., p. 32, pi. iii, figs. 1-6. 



^ Woodward, Geol. Mag., Dec. II, Vol. IX, p. 157, PI. IV, Fig. 1, 1882. 



■^ Clarke, Foss. Dev. Parana, 1913, pp. 97-101. 



^ Tchichatcheff, Asie Mineure, pt. iv, Paleont., 1866, p. 2, pi. i, fig. 8 (figure 

 not published). 



