NO. 3 CAMBRIAN AND OZARKIAN TRILOHITKS 99 



ISOTELOIDES 



Isoteloides Raymond, 1910, Ann. Carnegie Mus., 7, No. i, pp. 36, 67; 1910, 

 7th Rep. Vermont State Gcol., p. 223; 1912, Trans, and Proc. Roy. Soc. 

 Canada, 5, 3d ser., sec. 4, p. 115. 



Observations. — This genus appears to be characteristic of the 

 Beekmantown and Ordovician, occurring over a wide area in the 

 northern Rocky Mountains, in the Garden City limestone and beds 

 of similar age. Its presence in the upper Mons suggests the pdssi- 

 biHty of the uppermost beds here and there being referable to the 

 Beekmantown, but like Belief ontia it may occur in greater numbers 

 in the Ozarkian. 



ISOTELOIDES LAUTUS, new species 

 Plate 24, fig. 25 



Observations.— T\\\s cranidium and free cheek which may belong 

 together are referred to Isoteloides with reservation since the head 

 is quite narrow and has very narrow fixed cheeks. 



Formation and locality. — Ozarkian : (66v) Mons formation. Upper 

 Johnson Creek Canyon about one mile (1.6 km.) below divide on east 

 side of canyon, Sawback Range, 21 miles (33.8 km.) northwest of 

 Banfl', Alberta, Canada. 



ISOTELOIDES ? MALADENSIS, new species 



Plate 24, fig. 27 



Observations. — With better preserved specimens this species may 

 be transferred to Xenostegimn. The cranidium resembles that of 

 X. kirki and does not seem to be an Isoteloides because of its ex- 

 panded front. The pygidium appears to belong to the latter genus, 

 but it is broken away posteriorly so that the presence or absence 

 of a spine is uncertain. 



Formation and locality. — Upper Ozarkian ?: Near Malad, Idaho. 



ISOTELOIDES OCCIDENTALIS, new species 

 Plate 24, fig. 26 



Observations. — The cranidium and pygidium associated on a frag- 

 ment of rock appear to have the essential characters of Isoteloides. 

 The species differs from /. ivJiitfieldi Raymond mainly in its wider 

 cranidium, and the pygidium, so far as its characters are ascertain- 

 able, is very little different froin the one assigned to that species. 



Formation and locality. — Ozarkian ?, Mons formation {6yh.) North 

 fork Saskatchewan River, 3 miles (4.8 km.) south of Wilcox Pass, 

 Alberta, Canada. 



