ON TBILOBITES. 119 



Fam. 2(». ( 'hciruridn: — Pleura' with raised band. EycH finely facetted. Pygidinin hi^rncd, spino.so 

 III diii;ituled. Typ. ^ijcn. : '"'Af/ri/ri/s, Up. Cam., Dev. ; Pi ioplwn, V\t. S'i\.; Sjt/ia;rexochus,iii\.; 

 St(iur..cqiluiliis, Sil. ; Flacojuiria, Lr. Sil. 



NoTK. — The taniilies of lliis section arc moi'c m- loss closely connecte<l by the pocnliai- course of 

 the lacial .-futures, alike in all, and by thcii' typically eleven body-sc/^mentrf. The Knciinurida' and 

 Cliciruridte, are connected by their " bourrclcttcd " pleurae ; and this same condition — as well as their 

 t<pino>e character generally — connects the Chciruridse with the Acidasj)idn3 of tho next section. 



45 2. Ak-mati. — Hssentially broad-headed, spinoso forms, with pointed or spiny pleuijc, and small to 

 very small (commonly spine-bearing or digitated) pygidium. Body-scgmeids 1) to 20. 



Fam. 21. Acidaspidw. — Head, pleursc and pygidium, all spine-bearing. Body-segments 9 to 10. 

 Pleura; witli " bourrelet." Typ. gen. : Acidasjies, Sil., Dev. 



Fam 22. Faradoxidd'. — Head-shield ver}- largo and bruad, with horned angles and largo, anteriorly 

 expanded glabella. Body-segments 12 to 20 ; pleurte, furrowed, terminating in spines; Jiygi- 

 dium very small. Typ. gen. : Paradoxides, Cam. ; Hydrocephalus, Cam. : Telephus (?) Lr. Sil. 



§ 3. tlLOBOSi. — Glabella large and prominent, oval or globular, and unfurrowed. Thorax short, 

 with 5 to G segments. 



Fam. 23. Trinudeida: — Head-shield very largo, terminating in horns, and surrounded by a broad, 

 perforated border. Eyes commonly absent. Typ. gen. : Trinucleus, Lr. Sil. ; Dionide, Lr. Sil. ; 

 Microdiscus {?), Cam. 



Fam. 24. Ampyxid<c.—Ecad-sh'\G\d without perforated border. Glabella extended anteriorly into a 

 stiong spine. Eyes absent. Typ. gen. : Ampyx, Hi\.; Endymirma {f^iTJp. Cam. 



Fam 25. jKijUnidw. — Glabella very large and globular, extended anteriorly, in some Bpccies, into a 

 stout spine. P'yes abnormally developed. Typ. gen.: uE(jUna,'Lv.^i\. 



Note. — This latter family forms a connecting link between the (Jlobosi and the Oculosi. It 

 should, perhaps, be placed under the last-named section ; but it would apiiear to bo very closely allied 

 to tho Ampyxidic (notwithstanding Jie absence of eyes in that family) by its 5-0 body-segments, its 

 triangular pygidium, and its enormously developed iilabeila, which in some of its forms (e.g., ^E. 

 armaia, Bair.), extends forward into a distinct point or spine, much as in Ampyx. Whilst Barrandc 

 makes ^^glina the typo of a distinct family, Zittel places it under tho Asaphidic. 



§ 4. Oculosi. — Eyes enormously developed. Head-shield with horned angles. Pygidium very- 

 small, with 2-3 rings in its axis. 



Fam. 26. ^o/temiVi^uZtr.— Body- segments 5 in number. Typ. gen. : Bohemilla, Lr. Sil. 



Fam. 27. i?emo/>Ze«r('c/<i-.— Body-segments 11 to 13 in number. Typ. gen. : Eemopleurides, Lr. Sil., 

 Caphjjra, Lr. Sil. 



