294 bulletin: museum of comparative zoology. 



This name is proposed for the species previously identified with 

 " Asaphus" homalonotoides. Both cephalon and pygidium are similar 

 to those of that species, but the anterior end of the cephalon is hardly 

 elongate enough to justify a reference to Ectenaspis. It also seems 

 better to restrict Isoteloides to forms like the type, /. xchitfiiidi, which 

 has a rather distinctly outlined glabella and a narrow axial lobe. 



This species forms a connecting link between Isotelus and Ecte- 

 naspis. The anterior end of the cranidium, while not elongate, is 

 pointed, and though the glabella is not definitely outlined, some traces 

 of its shape can be seen, and a pair of faint glabellar furrows are 

 present on some specimens. 



Horizon and Locality :— A single cranidium of this species was 

 found by Mr. Narraway in the Leray-Black River at Ottawa, Ont., 

 and it is fairly common in the Glens Falls-Trenton at Pattersonville 

 and Smith Basin, N. Y. The holotype is in the Carnegie Museum. 



Isotelus rejuvenis, sp. nov. 



Entire specimen elongate oval, narrow, strongly convex. Cephalon large, 

 with short genal spines which in uncrushed specimens have their outer surfaces 

 nearly vertical. The facial sutures follow the same course as in /. iowensis, 

 being very close to, and parallel to the anterior margin. The eyes are very 

 small, elevated, situated a trifle more than their own length in front of the pos- 

 terior margin. The glabella is faintly outlined, constricted between the eyes, 

 and nearly smooth. 



Thorax as in /. iowensis, the dorsal furrows shallow, and the axial lobe more 

 than one third and less than one half the total Avidth. 



Pygidium elongate, narrow, with steep sides. The axial lobe is narrow, 

 faintly outUned except in young specimens, and without rings except for the 

 one on the anterior end. The pleural lobes show traces of several pairs of ribs, 

 two of which at the anterior end are very distinct. 



Measurements: — The holotjq^e is 105 mm. long; the cephalon is 38 mm. 

 long and 62 mm. wide; the pygidium is 46 mm. long and 55 mm. wide. 



This species differs from Isotelus iowensis in having smaller eyes, a 

 longer and narrower pygidium with two pairs of ribs at the anterior 

 end, and in having a less densely punctate shell. 



Horizon and Locality: — The species has so far been found only 

 in the lower part of the Maquoketa at Clermont and Elgin, Iowa, at 

 both of which places it is rather common in association with I. iowensis. 

 The holotype, M. C. Z. 1,586, was collected by the writer on a creek 

 about four miles west of Clermont. 



