NO. 2 MIDDLE CAMBRIAN MEROSTOMATA IJ 



edge of its inner third, or they may be of a lamellated structure 

 as shown by fig. i, pi. 3, fig. i, pi. 2, fig. 3, pi. 6. What is now 

 known of these branchial clusters recalls very strongly the lamellated 

 branchial fringes occurring in the cephalic portion of the trilobite 

 Calyiiicnc scnaria^ and in specimens of Neolenus scrratiis (see pi. 6, 

 figs. I and 2) associated with Sidneyia ine.vpectans. 



Observations. — In this preliminary notice of this remarkable crus- 

 tacean T have not attempted to describe many minor features of the 

 ventral appendages of the cephalo-thorax and abdomen. The com- 

 bination of characters shown by the conformation of the dorsal 

 shield and the grouping of the appendages indicates quite clearly a 

 transition form between the Trilobita and Eurypterida. In view of 

 larger collections being made available during the season of 1911 

 further description will be deferred. 



Formation and locality. — Middle Cambrian: Stephen formation, 

 Ogygopsis shale on west slope of ridge between Mount Field and 

 Mount Wapta, about 3800 feet above Field on the line of the 

 Canadian Pacific Railway, British Columbia, Canada. 



Genus AMIELLA, new genus 



What is known of this genus is contained in the description of 

 the type species. It differs markedly in form and surface from 

 Sidneyia. From Pierygotus, Eurypterus, and other genera of the 

 Eurypterida it differs in the character of the surface, epistoma, and 

 abdominal segments. 



Genotype. — Amiella ornata Walcott, which is associated with Sid- 

 neyia inexpectans in British Columbia. 



The generic name is given in honor of Dr. Henry M. Ami, of the 

 Geological Survey of Canada. 



AMIELLA ORNATA, new species 



(PI. 5, fig- 4.) 



Of this species only one broken specimen of the dorsal shield is 

 known. This shows that the body was elongate, narrow, and the 

 abdomen formed of a number of large segments of which remains 

 of seven are preserved ; also a part of the cephalo-thorax. 



Crust thin and compressed in the shale. 



Cephalo-thorax. — The portion of the cephalo-thora>i preserved 

 (it may be only the epistoma) has been turned about, the dorsal shell 

 of the cephalo-thorax having been loosened and displaced. If it is 



' Bulletin Museum of Comparative Zoology, Vol. 8, 1881, pi. 3, figs- i, 2. 



