202 



Pound in the lower Moscow shale, jit Sections 4 and 5 



(common); Encrinal limestone, at Section 5 (rare); between 



the Trilobite and StrophaJosia beds, in Avery's Creek, and 



on the Lake Shore (rare). 



Chonetes setigerus. (Hall.) (Fig. 107.) (Pal. X. Y., 



Vol. IV.. ].. li>l). PI. XXI.) 



Distinguishing ( 'haracters. — Semi-elliptical 

 outline; moderate convexity ; moderate num- 

 ber of rounded surface striae and vertical 

 s, ',!/'- ,,'v' ventral cardinal spines, of which three occur on each 



valve, x2(fromHall). side f)f t he beak. 



Found in the Hamilton shales, at Section 6, two to three 

 feet below the Encrinal limestone (very rare); seventeen to 

 twenty-one feet below the Encrinal. at Section 7 (rare); 

 Pleurodictyum beds, in Avery's Creek (occasionally); Transi- 

 tion shales and Marcellus shales, in Lake Shore Cliffs (not 

 very common ). 



Chonetes scitulus. Hall. (Fig. 108.) ( Pal. X. Y., Vol. 

 IV.. p. 130, PL XXI.) 



Distinguishing Characters. — Semi-oval outline ; somewhat 

 gibbous character; numerous surface stria*; numerouscardi- 

 nal spines (as many as twelve or fourteen being sometimes 



Fio. 108. Chonetes scitulus. Ventral (pedicle) and dorsal (brachial* views of a speci- 

 men, natural size : interior of pedicle and of brachial valves, enlarged (from Hall). 



indicated), which pass obliquely outward; interior of bra- 

 chial valve strongly pnstnlose, with abroad depression along- 

 tin' center, from which rises a slender median ridge; a similar 

 median ridge occurs in the interior of the pedicle valve. 



Found in the lower two feet of the Moscow shales, at Sec- 

 tions 4 and .1 (rare); in the Encrinal limestone (rare); 

 throughout the Lower (Hamilton) shales, at Sections 5, 6, 7, 

 8, and on the Lake Shore and in Avery's ('reek (often abun- 

 dant i : Transition shales, on the Lake Shore (rare). 



