406 



Arionellus CYLINDRICUS. (N. Sp.) 



Fig. 385. _ Fig. 38G. 



Fig. 385. — Arionellus ajlindricus. 



Fig. 3S6.—jli-ionellus subclavatus ; a, side view of the glabella. 



Description. — Glabella sub-cylindrical slightly narrowed from behind 

 forwards, the sides nearly straight and separated from the very prominent 

 cheeks by a deep furrow ; the front obtusely rounded or nearly straight. 

 The neck furrow is deep and rounded and the neck segment well defined 

 but apparently not very prominent. The posterior glabellar furrow is 

 well defined all across, parallel with the neck furrow for half the width of 

 the glabella and then directed obliquely forward on each side at an angle of 

 45° ; it is about its own width distant from the neck furrow. The next 

 furrows forward are situated a little in advance of the mid-length of the 

 glabella ; they are slighty oblique and their inner extremities are separated 

 by about one-third the width of the glabella. In front of these are two 

 other furrows on each side very inconspicuous and not always visible. The 

 anterior margin of the head consists of a narrow elevated ridge separated 

 from the front of the glabella by an angular groove of about its own width. 

 From the summit of the terminal ridge the margin descends with an abrupt 

 slope so that on a front view the head appears to be bounded by a flat 

 nearly vertical band, the width of which is equal to rather more than one 

 half the elevation of the glabella. The surface appears to be smooth or 

 finely granular. Eyes, fixed cheeks, thorax and pygidium unknown. 

 Length of longest head seen three and a half lines ; width of glabella about 

 two lines at neck segment and a little less at the anterior extremity. The 

 form of the glabella of this species is almost exactly like that of Dikehce. 

 phalus granulosus. (Owen.) [See Geo. Rep. Wisconsin, Phi, Fig. 7.] 



Limestone, No. 1, not common. 



Arionellus subclavatus. (N. sp.) 



Fig. 386,— a. 



Description. — Glabella as long as the head, separated from the front 

 margin by a narrow groove only, strongly convex and elevated in the 

 anterior two-thirds, less convex, more depressed, and somewhat narrower 



