822 Dr. F. R. Gowper Reed — The genus Homalonotus 



Type. — Homalonohis Brongniarti (Desl.). 

 Range. — Lower Ordovician. 



Distribution.— N. France, Cornwall, Shropshire, Bohemia? 



Examples. 



H. Deslongchampsi, de Trom. H. Barroisi, de Trom. 



H. Bonissenti, Mor. H. biserratus, sp. nov. 



H. serrahis, de Trom. H. quadratus (Hicks). 



H. Vicaryi, Salt. ? H. bohemicus, Barr. 



H. besnevillensis, Bigot. ? H. draboviensis, Novak.-' 



H. incertus, Bigot. ? H. medius, Barr. 



H. Morierei, Bigot. 



Remarks. — This section comprises the earliest representatives of 

 the genus Ho^nalonotus. There is a close connexion between it and 

 Pompecki's Synhomalonotus, through which the genus is related to 

 Calymene. 



2. Calymenella, Bergeron. 



Head-shield triangular, produced in front into a rostrum. Facial 

 sutures uniting in front in regular continuous curve at base of 

 rostrum and inside margin. Pygidium semicircular, transverse, 

 composed of few segments, distinctly trilobed ; axis and pleuraj well 

 marked. 



Type. — H. (Calymenella) Boisseli (Bergeron). 



Range. — Ordovician. 



DiSTKiBUTlON . — France . 



Example. — H. (C.) Bayani (De Trom. & Lebesc). 



Eesiarks. — The peculiar distinguishing feature of this subgenus 

 is the possession of the rostrum, the precise nature of which has not 

 been thoroughly investigated ; but it seems to be merely a mucli 

 elongated narrow prora, as in Dipleura, and to be wholly pre-sutural 

 in origin and perhaps epistomal in nature. The head-shield and 

 glabella in other respects seem to resemble JEohomalonotus, and the 

 pygidium is unmistakably of the same type. Bergeron regarded the 

 two species mentioned above as constituting a distinct genus, but 

 Pompecki considered that it was only a subgenus of Homalonotus. 



3. Brongniartella, nom. prop. { = Bro7igniartia (pars), Salter, 

 section 1, non Leach, nee Eaton). 



Head-shield rounded, semi-elliptical or semicircular, wider than 

 long. Facial sutures uniting close to anterior margin or on margin 

 in regular wide curve, and posteriorly cutting lateral margins nearly 

 at genal angles. Glabella urceolate, rhomboidal, or subconical, 

 generally lobeless. Pre-glabellar area of moderate width ; pre- 

 sutural band very narrow or wanting. Thorax with trilobation more 

 or less indistinct ; axis wider than pleural portions. Pygidium 

 rounded, semi-oval or parabolic, composed of nine to twelve segments ^ 

 axis distinct; pleurae continued nearly to margin; border usually 

 developed but not defined ; doublure flat, horizontal, closely in- 

 folded, of nearly uniform width. 



Type. — H. bisulcatus, Salter. 



Range. — Middle and Upper Ordovician. 



Distribution. — England. 



^ Novak, " Zm- Kennt. bohm. Trilob." : Beitr. Palseont. (Est. Ungarns,. 

 p. 27, pi. viii, figs. 9a-c, 1884. 



