324 Dr. F. B. Coiuper Reed — Tke genus HoTnalonotus. 



obsolete, bat segmentation of axis and pleurae distinct. Doublure 

 widening posteriorly. 



Type. — H. Knighti, Konig. 



Kange. — Silurian (Ludlow). 



Distribution.— Northern Europe. 



Example. — ? H. Johannis, Salt. 



Remakes. — This is undoubtedly a highly specialized group in the 

 genus. A similar sudden bend in the anterior course of the facial 

 sutures is found in Digonus (q.v.), and the tendency to a projection of 

 the epistorae is seen less developed in Burmeisteria (q.v.). The vrhole 

 head-shield of the type-species is, however, marked by very unusual 

 modifications. It is doubtful iiH. Johannis can be closely associated 

 with it, in spite of its tricuspid front, as the pre-glabellar portion is 

 different; but the pygidia of the two species are very similar. As 

 regards the thoracic and pygidial characters of Koeyiigia it is easy to 

 see their general resemblance to Trimerus. The specimens of the 

 type-species in the Ludlow Museum which I have been privileged to 

 examine by the kindness of the Curator exhibit the characteristic 

 features with great clearness, being unusually well preserved. 



6. Burmeisteria, Salter (sens, restr,). 

 Head-shield more or less triangular. Facial sutures convergent 

 anteriorly and uniting by a double sigmoidal commissure close to 

 front margin, and posteriorly cutting lateral margins in front of 

 genal angles. Pre-glabellar area well developed. Paraglabellar 

 areas distinct. Glabella occasionally lobed. Epistome projecting 

 in front of anterior margin of head-shield as median pointed process. 

 Pre-sutural area very narrow. Thorax with wide, ill-defined axis ; 

 trilobation indistinct. Pygidium triangular, acuminate, strongly 

 convex from side to side, composed of many segments ; axis and 

 pleurae more or less distinct. Sui-face of head-shield, thorax, and 

 pygidium frequently ornamented with more or less regularly disposed 

 large tubercles or spines. 



Type. — H. Herscheli (Murchison). 

 Eange. — Lower Devonian. 



Distribution. — South Africa, South America (including Falkland Islands). 



Examples. 

 H. quernus, Lake. H. agrestis, Schwarz. 



H. colossus, Lake. H. liorridus, Schwarz. 



H. perarmatus, Freeh. H. lex, Schwarz. 



H. hijppocampus, Schwarz. H. noticus, Clarke. 



Remarks. — This subgenus appears to be limited to the Southern 

 Hemisphere. As far as the thorax and pygidium are concerned, its 

 relations are with Trimerus, but the anterior course of the facial 

 sutures seems intermediate between Trimerus and Kx7iigia. The 

 spinosity, which is very irregularly developed in the species, cannot 

 have as much importance attached to it as some authors have 

 maintained. 



7. Digonus, Giirich. 

 Head-shield transverse or sub triangular. Middle-shield with 

 anterior lateral angles rectangular, obtuse, or projecting, and with 

 anterior margin truncate, straight, or slightly concave. Pacial sutures 



