BELTELLA. 103 



a rather broad margin, produced into genal spines. The glabella is quadrate or 

 conical, truncate or rounded in front, separated from the marginal furrow by a 

 frontal limb as wide as, or wider than, the margin. It is probable that the outer 

 surface of the test of the glabella was almost devoid of furrows ; but internal casts 

 usually show two pairs, the posterior pair being very oblique and nearly reaching 

 the neck-furrow. The facial suture starts at the outer edge of the anterior 

 margin, close to the middle line, and runs very obliquely outwards across the 

 margin ; from the inner edge of the margin it turns inwards to the eye and thence 

 outwards to the posterior margin, which it cuts well within the genal angle. The 

 thorax, so far as is known, consists of twelve segments ; all the pleurae, even those 

 of the hinder end of the body, have the outer part bent down and faceted ; in the 

 anterior segments the terminations appear to be rounded or bluntly pointed, in 

 the later segments they are falcate or spined. In front the axis is as wide as, or 

 wider than, the pleurae ; but posteriorly it becomes narrower than the pleurae. 

 The tail is small and entire. 



Many of these characters are to be found in Devine's Olenus? logani 1 (for which 

 he suggested the generic name Loganellus) and also in Cr&picephalus (Loganellus) 

 haguei, Hall and Whitfield. 2 The general shape is similar, the number of thoracic 

 segments is the same and the pleurae are of the same type, and the facial suture 

 runs outwards in front of the eye as well as behind it. Both these species have 

 since been ascribed by American palaeontologists to Ptychoparia, and by Brogger 3 

 to Liostracus, and the use of the name Loganellus has long been discontinued. 



In Beltella, however, the eye is placed farther forwards than in either of these 

 forms, and the ocular ridge is much less distinct ; but probably the most important 

 difference is in the facial suture. In Ptychoparia and Liostracus, and apparently 

 in Loganellus logani and Grepicephalas haguei, the facial suture crosses the anterior 

 margin almost at right angles, and if the sutures of the two sides meet, it must be 

 on the under surface ; in Beltella the anterior branches of the facial sutures diverge 

 forwards from the eye, but when they reach the margin they again curve inwards, 

 cross the margin very obliquely and meet in the middle line on the upper surface of 

 the body — as in DiJcelocephalus. Behind the eye the facial sutures in Beltella are 

 less divergent and make a smaller angle with the axial line than in the forms 

 referred to. 



The species described by Whitfield 4 as Angelina hitchcocJci, and afterwards made 



1 Description of a new trilobite from the Quebec group, Can. Nat. and Geol., vol. viii (1863), 

 p. 95; reprinted Greol. Surv. of Canada (1863), p. 21 ; see also Billings, Pal. Foss., vol. i, p. 200. 



2 U.S. Geol. Explor. 40th Parallel, vol. iv (1877), p. 210, pi. ii, figs. 14, 15. Walcott's observations 

 on Crepicephalus show clearly that Hall and Whitfield's species do not belong to that genus; see Bull. 

 U.S. Geol. Surv., no. 30 (1886), p. 206; Mon. U.S. Geol. Surv., vol. xxxii, pt. 2 (1899), p. 459 ; 

 Smithsonian Misc. Coll., vol. lxiv, no. 3 (1916), p. 199. 



3 Geol. Foren. Stockh. Fork, vol. viii (1886), p. 202. 



* Bull. Amer. Mus. Nat. Hist., vol. i, no. 5 (1884), p. 148, pi. xiv, fig. 13. 



