Vol. 50.] OLEtfELLTJS-ZONE OF THE NORTH-WEST HIGHLANDS. 675 



Fig. 11. 0. reticulatus. Detached body segment from posterior part of body, 



nat. size, to show rudimentary spine on axis. 

 Fig. 12. 0. reticidatus, nat. size. Showing several body-segments and the 



nature of the articulation of the telson. Same locality. M. 4077 d . 

 Fig. 13. 0. reticulatus, nat. size. Detached labrum, supposed to 'belong to 



an individual of this species. ' Fucoid Beds,' Allt an Righ Jan, 



Dundonnell, Ross-shire. 

 Fig. 14. 0. reticulatus. Portion of largest individual observed. 



Plate XXXI. 



Fig. 1. Olenellus reticidatus, nat. size. Shows the first two body -segments tele- 

 scoped into the head-sbield, the body being bent over at the eighth 

 segment. Telson seen where the pleura or the left side have broken 

 away, with counterpart. From ' Fucoid Beds,' Meall a' Ghubhais, 

 Kenlochewe, Ross-shire. M. 4142 d . 



Fig. 2. 0. reticulatus, nat. size. Counterpart of fig. 1. 



Fig. 3. 0. reticidatus, nat. size. Distorted by the glabella being driven obliquely 

 over the cheek. Same locality. M. 4l)78 d . 



Fig. 4. 0. reticulatus. Counterpart of fig. 3. 



Fig". 5. 0. reticulatus, nat. size. Same locality. M. 4U91 d . 



Fig. 6. 0. reticulatus. Counterpart of part of fig. 5. 



Fig. 7. 0. reticulatus, nat. size. Left pleuron of third body -segment. Same 

 locality. 



Plate XXXII. 



Fig. 1. Olenelloides armatus. Enlarged 3 diameters, showing the outer side of 



the right half. ' Fucoid Beds,' Meall a' Ghubhais, Kenlochewe, Ross- 

 shire. M. 4111 d . 

 Fig. 2. 0. armatus. Enlarged 3 diameters, showing the inside view of tho 



leftside. Counterpart of fig. 1. M. 4111 da . 

 Fig. 3. 0. armatus. Enlarged 3 diameters. Dorsal view of 1 and 2 combined. 

 Fig. 4. 0. armatus. Enlarged 3 diameters. Broad head-shield. Same locality. 



M. 4116 d . 

 Fig. 5. 0. armatus. Enlarged 3 diameters. View of inside of elongated head" 



shield. Same locality. M. 4117 d . 

 Fig. 6. 0. armatus. Enlarged 3 diameters. Medium form of head-shield. 



Same locality. M. 4127 d . 

 Fig. 7. Olenellus intermedins. Enlarged 3 diameters. Head-shield. Same 



locality. M. 4149 d and 4149 da . 

 Fig. 8. 0. Lapworthi, nat. size. Small head shield, to compare with figs. 4-7, 



showing that in this species the genal spine is at the posterior angles 



even in young individuals. Same locality. 

 Fig. 9. 0. Gilberti (Walcott), after Ford and Walcott. Young stage, whero 



the genal spines are placed far in advance, and given off in almost 



the same straight line as the anterior margin. 

 Fig. 10. 0. Gilberti (Walcott), after Ford and Walcott. Young stage, in which 



the genal spines have travelled a little farther round than in fig. 9. 

 Fig. 11. Mesonacis (0.) asaphoides (Emmons), after Walcott. Young stage, in 



which the spines are still retained at the pleural angles. 

 Fig. 12. Holmia ( U.) Kjerulfi (Linnarsson), after Holm, showing the head-shield 



and the first two free body-segments. Portion of the glabella is 



removed, to show the labrum in position beneath. 

 Fig. 13. Spine of Olenellus gigas bored by annelid ? Nat. size. Meall a' 



Ghubhais, Kenlochewe, Ross-shire. 

 Fig. 14. Counterpart of fig. 13. 

 Fig. 15. Spine of Olenellus, bored by annelid? Nat. size. Same locality. 



Q. J. G. S. No. 200. 3 a. 



