56 PEOCEEDINGS OP THE GEOLOGICAL SOCIETY. 



outwards, following nearly the outline of the cheeks. Their upper 

 end is very close to the glabella at its widest part. 



The cheeks are triangular, the margin smooth ; the surface within 

 it is scrobiculate, but not deeply so. Their margin, which is wide at 

 the base of the spines and sides, is almost entirely lost in front by 

 the overlapping of the large glabella. This is only the case in fully 

 grown specimens (fig. 2.) ; in the young (figs. 8, 9, & 10) the margin 

 is equal all round, and a considerable space, also, separates the 

 glabella from the anterior margin. This space gradually diminishes 

 as the individual grows ; and the glabella enlarges until, as in the 

 fully grown specimen (fig. 2), the margin becomes completely ob- 

 literated. 



The labrum (fig. la) is curved, expanded at the base, and trun- 

 cate at the end, with the angles rounded. 



The thorax consists of nineteen rings; axis convex, tapering, 

 and rather narrow, being about a third less than the width of the 

 pleurjB (including spines) anteriorly, whilst posteriorly, for the last 

 six or seven segments, it is scarcel}^ half as wide, the ]3leura3 having 

 increased in length, whilst the axis has been gradually tapering. 

 The pleurae are compressed and deeply grooved obliquely to a little 

 beyond the base of the spines ; the upper fouiteen terminate in 

 short spines, which turn abruptly backwards, and at about the same 

 angle. In the hindmost pleurae the spines are somewhat lengthened, 

 but are still very short indeed for this genus, and are exactly like 

 the two front pleurae of the tail. The latter is composed of two 

 nearly free segments, with short spinous pleurae (fig. 5), and an 

 appendix, which is almost circular and has one pair of lateral ribs 

 only. It has a broad axis, marked by five annulations, the hinder 

 one being much elongated, and indented slightly along the middle 

 of its length. The limb of the broad circular appendix (fig. 6) is 

 quite distinguished from the two front pleurae, and is depressed, and 

 marked by two furrows, which terminate in the wide margin. The 

 upper pleurae are grooved nearly to their tips. Margin of limb 

 strongly marked, and somewhat raised. — H. Hicks. 



The close observer can hardly fail to be struck with the sort of 

 intermediate character borne by this species. It reminds us almost 

 equally of Parado.vldes and Anopolenus. The shortened spines to 

 the body and tail, the long, narrow, and strongly margined eye, 

 the transverse, equal, parallel side-lobes of the glabella, the distinct 

 anterior margin to the head (on the young specimens at least), the 

 squarish, not wide, truncated labrum, and the compound tail, all 

 tend to connect this old species, first with such further-developed 

 forms as ^QAnopolenus{^)oi Farado.TidesLovenijAngelin, of Sweden, 

 and, through them, with Anojpoleniis itself. 



In speaking of the compound tail, I would not be too confident 

 that the two pleurae really form part of it. But we cannot deny 

 that several of the species really have a pair of long-spined pleurae 

 attached to the upper border of the tail itself, though their connexion 

 with the rounded or squarish appendix is not evident in general. In 



