< , ,i,.\ 



the t|iie-tion. are they really congeneric witli tin- typical >pi < .-pend-. I *hould 



say, entirely upon tin- -igniticaiice we attach to the presence or absence of the 

 marginal frill. Hclieving that further inve-t Cation- arc de-irable. I -hall not 

 tint to decide tin- .|'i.--i :..i; now. In tin- meantime the now species may be 

 known a- a doubtful l>icr<im-llii, while the other- had le-t remain when' Prof. Jones 

 ha- |>larrd them. 



l>i 'i -/-. 



i i.\ 1 1 \i.i\. i i.. - i -j-. 



\\ ittiniil I. mil : tln< nun. 



ii Ininl.T, l.'UKlli I - nun.: liu-lit 1 i'-J nun. 



Vahe-ol.l. i^'ht ilnr-ally. roiinle<l \entrally ami at the ends, the latter 



nearly e|iial. 'I'wo lar^e. -iilie.|iial. diver^injf. horn-like (intcesses, angular in croes- 



n. ari.-e liehind the center of the dorsal half and project far beyond the dorsal 



n their liases a suhoval depre--ion; lower half of posterior horn with a 



laix'e rounded -welling. Outline of valves marked liy a sharply defined, linear ridj^e; 



beyond tin- a wide hut very thin. >mooth horder or frill, usually I'ending outward 



at theed^re; horder narrowe-t anteriorly, widest below. 



Th i- species is so easily recognized by its "horns," that comparisons are quite 

 unnecessary. 



./ locality \. -.-. :m<l middle thlrdsofll -ishalesi- :lu ami Ithlul- 



dii-l Minnt-ajx 



I IK i 



41 



mm.: hitftit 0.8 nun.: thickm- u.4*> mm. 



This species is similar to I>. A;',/-;i/'> hut the valves are a little longer, and the 

 "horn>" hejjin lower down on the valves ami are not carinated, while the posterior 

 one i- shorter, ami >eem- not to extend beyond the rounded swelling. The border 

 al-o seem- not to have been developed anteriorly, while along the ventral edge it i- 

 ii-ually replaced by a >erie- of -pine-. 1'o-teriorly it ha- about the same width as 

 in If. liiriirni*. but i- ornamented with radial furrow- in-tead of I, em;: plain. 



Formation unit tofilit; third. .f ' il.> (Khinldl neapolU. ^' 



