,'}i<S Annals of the Cakne(;ie Museum. 



Descrii'iion. 



Cephalon. — Cranidium small, regularly rounded and abruj)! in 

 front. Dorsal furrows short and faint, turning out slightly at the 

 anterior end. Eyes small, situated well back and far apart. Surface 

 very punctate with the exception of two small spots between the an- 

 terior ends of the dorsal furrows and the eyes. These are smooth. 

 The front slope is covered with fine concentric wrinkles, between 

 which are rows of punctre. 



Thorax of nine segments which are very narrow and turn down and 

 a little backward at the sides, but are straight and flat on the dorsal 

 region of the pleura. Axis strongly convex and about one third the 

 width of the thorax. It tapers very gradually, and in our specimen 

 is 4.5 mm. wide at the front end of the thorax, and 4 mm. wide at 

 the i)ygidium, thus losing only .5 mm. in a length of 6.75 mm. 

 Surface punctate. 



Pygidium almost semicircular, gently convex. Axis is defined for 

 a short distance, but is not prominent. Surface covered with very 

 numerous shallow punctse. 



In the complete specimen the pygidium is drawn up at right angles 

 to the axis of the body so that it is hardly visible from the dorsal 

 aspect. It can not be determined from our material whether this is 

 the natural position, or whether it may be due to crushing. The 

 cephalon is distorted, making one eye appear much more prominent 

 than it should, while the other is removed. The entire specimen is 

 14 mm. long and 12 mm. wide at the genal angles. The cephalon is 

 7.5 mm. long and the thorax and pygidium, if flat instead of being 

 drawn up, would make the total length 19 mm. 



Locality. — The type specimen, which is in the collection of the 

 writer, is from the middle of the Crown Point section. Other speci- 

 mens have been found in the upper layers on Valcour Island. 



Illaenus bayfieldi Billings. (Plate 13, figures 11, 12.) 



Ilhrnus /?(nyf(7(// Billings, 1S59, Canadian Naturalist and Geologist, volume IV, page 

 369, figures 4-6. 



This is the only one of the seven species of trilobites described by 

 Billings from the Chazy limestone at the Mingan Islands which has 

 not yet been found in the Champlain Valley. Professor Whiteaves 

 very kindly loaned two of the typical specimens, figures of one of 



