4 



BRITISH FOSSILS. 



3. Var. Blumenhachii vera, 0. pulchella, " undique punctis elevatis 

 sparsis," the axis hardly tuberculate at the sides ; small. Gottland. 



Of these three forms the first is the most doubtful. Dalman has pro- 

 bably given a figure of it, bad in all points of detail, in his table 1, fig. 2. 

 This figure seems a little to resemble our species in the rather narrow- 

 axis, and distant fulcrum, and there is no indication of bifid ribs to the 

 tail ; however, the snout is not produced at all, the axis of the tail is 

 also broad and convex, so that it probably is intended for the common 

 species. Of his var. pulchella (tab. 1, fig. 3), we have seen specimens 

 in the cabinet of Sir Roderick I. Murchison. They are dwarfs of C. 

 Blumenhachii, and, like it, have scattered tubercles, a large glabella, 

 and convex axis. But the description of var. 2 in so many respects 

 agrees with the subject of our plate, that we have adopted the term 

 tuberculosa as a specific name for it. The close minute scabrosity is 

 particularly alluded to by Dalman. Even if the identification be 

 incorrect, it will not involve any confusion of nomenclature. No 

 recognizable figure of this species appeared till the publication of the 

 " Silurian System," in which, at pi. 7, f. 5, a Burrington specimen is 

 figured, and in the description the knots on the axis are mentioned as 

 variable. 



British Localities and Geological Position. — Wenlock shale to 

 Upper Ludlow Bocks. Upper Silurian beds, Underbarrow, near 

 Kendal, Westmoreland (Prof. Sedgwick). It abounds in nodules of the 

 Wenlock shale at Burrington, Shropshire, from whence thousands of 

 specimens have been distributed through collections. Small specimens 

 are plentiful at Usk, Monmouthshire, in Upper Ludlow Rock ; in 

 neither case associated with the more common C. Blumenhachii. 



Foreign Distrihution. — There is much reason to believe, as before 

 stated, that it occurs with the better known species in Gottland. 



Explanation of Plate VIII. 



Fig. 1. Full-grown specimen from Burrington ; the head and tail a little bent down. 

 Fig. 1*. A specimen from the same locality, partially rolled up, but open sufficiently to 

 show the hypos tome or mouth- piece attached to the rostral shield a. 

 Fig. 2. Extended specimen from the same locality. 

 Fig. 3. Dissected head ; k is the reflected front. 



Fig. 4. Body segment separated, shows the nodular axis, and the distant fulcrum. 



Fig. 5. Body segment seen in profile. It shows the depressed form of the body. 



Fig. 6. Hypostome highlj'^ magnified. 



Fig. 7. Magnified portion of the general surface. 



Fig. 8. Young animal from Usk. 



Fig. 8 a. Tail of ditto magnified. 



J. W. Salter. 



June, 1849. 



