32 



G. C. Ci'ich — Pcricyclusfascicidatus, M'Cujj. 



last whorl is occupied by the body-chamber ; the last three suture- 

 lines are clearly visible at the commencement of the outer whorl 

 (see accompanying figure). Towards the anterior end of the body- 

 chamber one side of the shell bears traces of an injury during the 



Fig. 4. — Suture-liue of Pcrici/cliis fasckulatun. Drawn of the natural size from 

 the last septum (at a radius of 13-5 ram.) of an example in the collection of 

 Dr. Wheeltou Hind, from the Carboniferous Limestone of Bradbourue, about 

 2 miles north of Kniveton, Derbyshire. 



life of the animal that has interfered somewhat with the regular 

 sculpturing of the shell, but the original number of the ribs crossing 

 the periphery can be ascertained to be 36. As will be seen from the 

 dimensions, this specimen is more widely umbilicated than the 

 example from Kniveton. 



The other specimen consists of about one-half of the outer whorl 

 of a rather more finely sculptured example of about the same 

 diameter as the fossil just described, that has been distorted into an 

 elliptical form. It exhibits no septa, and most likely formed part of 

 the body-chamber ; the ribbing is a little irregular at the anterior 

 part of the specimen, but in the half-whorl there appear to have 

 been about 22 ribs on the central portion of the peripheral area. 



The following table enables the type-specimen of M'Coy, the 

 British Museum example from Clane, and the English examples 

 referred to in the present paper to be more readily compared with 

 one another, the specimens being arranged according to their 

 respective diameters. (i) is the example from Beeston in the 

 Museum of Practical Geology [No. 8860] ; (ii), the specimen from 

 near Matlock in the same collection [No. 6696] ; (iii), the nearly 

 complete example from Bradbourne in the collection of Dr. Wheelton 

 Hind ; (iv), M'Coy's type-specimen of ' G.' fasciculatiis in the Museum 

 of Science and Art, Dublin; (v), the specimen from Kniveton in the 

 British Museum Collection [No. C. 7961] ; (vi), the example from 

 Clane in the same collection [No. C. 5933]. The measurements are 

 in millimetres. 



Diameter of shell 



Radius of shell 



Width of umbilicus 



Height of outer whorl . . . 

 rhickness of outer whorl 

 Height of outer whorl 

 above preceding whorl. 

 f^o. of ribs in outer whorl 



20 (100) 



12 (60-0) 



7 (35-0) 



6-5 (32-5) 



16 (80-0) 



c. 30 



32 (100) ,84- 

 18 (56-2) 20 



12 (37-5) 

 12 (37-5) 

 21 (6o-6) 



r.9(28-l) 9 

 34 36 



(100) 

 (57-9) 



16-5 (47-8) 

 11 (31-8) 

 21-5 (62-3) 



(26-0) 



From the above table of measurements, it will at once be seen, 

 firstly, that the Beeston example is relatively thicker than the others, 

 and secondly, that there is some irregularity in the height of the 

 outer whorl and of the width of the umbilicus in specimens iii and iv. 

 In iii (Dr. Wheelton Hind's specimen from Bradbourne) the umbilicus 

 seems to be relatively wider and the height of the whorl narrower 



