6 



BRITISH FOSSILS. 



of the head, a nearer approach is made to the typical species of thd 

 section Trapelocera. 



The common two-spined Wenlock species (most inadvertently 

 connected with it in the " Memoirs Geol. Surv./' vol. ii. pt. 1. pi. 9. 

 fig. 4) has much more remote eyes, and the glabella lobes quite 

 fused externally with the cheeks. It probably belongs to the same 

 section with those now described, and if not identical with the 

 A. (Trapelocera) vesiculosa, Beyrich, is very closely allied to it. 

 Mr. Fletcher, of Dudley, has named it A. Barrandii, and will 

 publish it shortly. It must form the subject of a future plate, as it 

 is the type of the sub-genus Trapelocera. 



Professor M'Coy, in his work, has shown that this has nothing 

 in common with the Od. hispinosa, Emmr., a name proposed by 

 him to be substituted for 0. ovata, by which he formerly (Disser- 

 tatio Inauguralis, 1839,) designated his species; the name in that 

 case refers to the double spinous terminations of the pleurae, not to 

 the projections from the neck, which appears to be smooth and 

 unarmed. 



British Locality and Geological Position. — Llandeilo Flags. 

 In the limestone of the Chair of Kildare, county of Kildare, which, 

 by its numerous fossils, is exactly referable to the age of that of 

 Llandeilo and Bala. [Coll. Geol. Survey.] 



Explanation of Plate VI. 



Fig. 1. Head of Acidaspis Jamesii, natural size. Newtown, "Waterford. 

 Fig. 1*. The same magnified. 



Fig. 2. Body ; shows also portion of the head. Same locality. 



Fig. 2*. Portions of the same, magnified ; a, external surface of one of the thorax rings j' 



and b, the 12-spined tail. 

 Fig. 3. Interior cast of another specimen from the slates of Wexford. This specimers 



is the same as that figured Mem. Geol. Survey, vol. ii. pt. 1. pi. 9. f. 5. 

 Fig. 3*. Shows portions of the same, magnified ; a, the cheek with its spines ; b, the 



tail with its marginal spines. 

 Fig. 4. Acidaspis bispinosus, M'Coy, nat. size. Chair of Kildare. [Survey Coll.]* 

 Fig. 4*. The same, magnified. 

 Fig. 5. Section of the gibbous head. 



Fig. 6. Tubercles and granules of the surface, highly magnified. 



Notice of one or two other British Species. 



3. There is a species found in the Bala Limestone, of which we have only a portion of 

 the head. It differs from A. Jamesii in having fewer and larger tubercles on the head, and. 

 the central glabella lobe broader in proportion to the side lobes ; it is too imperfect to 

 name. 



4. The head of a small species, about equal in size to our figured specimens of A. bi- 

 Spijiosusj occurs with it very rarely in the Chair of Kildare, Ireland. The central glabella 



