4 F. R. Coivper Reed — Siome Wenlock Species of Lichas. 



is subquadrate rather than semicircular ; the first two pairs of 

 lateral spines (i.e. the pleural points) are moderately developed, 

 and equal or subequal in size ; the third pair of spines is developed 

 as in the variety wenlockensis, being stronger and stouter than the 

 others ; the fourth pair of spines is reduced in size, and slender, 

 and usually rather closely placed to the third pair, leaving the 

 median portion of the posterior margin free of spines and only 

 armed with small prickles. In other respects this variety resembles 

 that above described. Both differ from the type-form by the 

 subquadrate rather than semicircular shape of the pygidium, and 

 by the specially strong development of the third pair of marginal 

 spines. This second variety may be termed obtusicaudatiis. 



Salter attributed both these varieties of Z. angliciis to Z. hirsutus, 

 as his labels and Catalogue show (Cat. Camb. Sil. Foss. Woodw. Mus., 

 p, 130, a 961, a 963, a 964), but they differ completely from it, as 

 a reference to Fletcher's figured, specimens and the descriptions of 

 that species at once proves. 



The ' angularity ' of the head-shield upon which Fletcher remarks 

 in one specimen (figs. 3, 3a, pi. xxvii) is caused by the sudden bend 

 in the front margin of the free cheek, just outside the point where 

 the facial suture cuts the border. This projection of the middle 

 portion of the head-shield is very well marked in some specimens 

 of the type-form and in the variety wenlockensis, and is indicated in 

 the restoration of the front border by Fletcher {op. cit, pi. xxvii his, 

 fig. la). It appears to be a characteristic and constant feature, 

 being noticeable wherever that portion of the head-shield is preserved, 



Lichas (Cokydocephalus) hiksutus (Fletcher). (PI. I, Figs. 3, 4, 5.) 



L. hirsutus, Fletcher {pars): Q.J.G.S., 1850, vol. vi, p. 236, pi. xxvii, figs. 6, 6« ; 



pi. xxvii bis, figs. 2, 2a {non pi. xxvii, figs. 7, la). 

 L. Bucklandi, Fletcher {pars) : ibid., pi. xxvii, figs. 1, \a, lb {non cet.). 



There are three specimens ascribed to this species by Fletcher 

 and figured by him, all of which are in the Woodwardian Museum. 

 Excluding the remarks on the specimen figured on pi. xxvii, figs. 7, la, 

 the description of the species given by Fletcher is fairly accurate 

 and complete so far as it goes, but the figures (pi. xxvii, figs. 6, 6a ; 

 pi. xxvii his, figs. 2, 2a) show such differences that they might be 

 thought to represent distinct species. The specimens, however, 

 from which these figures were drawn are in reality closely similar, 

 and do not exhibit more than the customary amount of variation. 

 The specimen on which figs. 6, %a, pi. xxvii were founded is so 

 imperfect that it shows Fletcher used other specimens together with 

 it in order to draw up his description of the species. There is na 

 distinctly raised border round the pygidium, the appearance in 

 Fletcher's figured specimen (pi. xxvii, fig. Qa) being due to unequal 

 crushing. Other specimens show that the relative length of the 

 axis slightly varies, and also the number of tubercular rings 

 upon it. 



A well-preserved complete specimen in the Woodwardian Museum 

 showing head, thorax, and pygidium attached, and several other less 



