OLENELLUS AND OTHER GENERA OF MESONACIDzE 299 



and 20, also the size and length of the palpebral lobes which are 

 -elevated and joined to the first glabellar lobe by a narrow ridge. 

 The palpebral lobe [figs. 17, 19] is short and much like that of 

 JJ'aiiiicria zvalcottanns [pi. 30, fig. i]. From the posterior end 

 of the palpebral lobe a narrow furrow on the interior of the test 

 curves backward and then outward and backward to the posterior 

 margin, following in its course the position of the facial suture of 

 Paradoxidcs spiiiosiis Boeck [Barrande, 1852, pi. 12. fig. i]. Oc- 

 cipital ring strong, rounded, and with a small median node near the 

 posterior margin. 



The hypostoma is of the same general character as that of Cal- 

 .Icn'ia brliggcri [pi. 27, fig. 2] and C. crosbyi [pi. 28, fig. 6], and 

 differs from the hypostoma of JVonncria [pi. 31, fig. 9] in having a 

 ■smooth, rounded frontal margin. 



Surface know^n only from a few fragments of the test adhering 

 to the specimens illustrated by figs. 20 and 23. These show the char- 

 acteristic irregular, elevated ridges of the surface of Holinia. also 

 fine, rather sharp granulations. A cephalon 2 mm. in length [fig. 

 24] is strongly convex and with unusually elevated prominent pal- 

 pebral lobes that merge into the first glabellar lobe in a manner 

 similar to those of the young 0/ Ellipfoccphala asapJioidcs [pi. 25, 

 fig. 10]. 



Diiiicnsions. — These are shown for the cephalon by fig. 21, which 

 is reproduced from a photograph, natural size. 



Observations. — This is a very interesting species of the Meso- 

 nacidae, and it is to be regretted that there are no entire specimens of 

 the dorsal shield. JWinncria ? gracilc is distinguished by its slender 

 conical glabella from W. zvalcottanus. It resembles the latter species 

 in having short, elevated palpebral lobes connected with the first lobe 

 of the glabella by a strong occular ridge. Its slender glabella with 

 the narrow first lobe is more like that of Calhz'ia [pi. 2^, fig. i ; pi. 

 28, figs. 3 and 8] than that of IVanncria [pi. 30, fig. i ; pi. 31, figs. 

 I, 5, 6], which has a rounded, expanded anterior lobe to the glabella. 

 It is not known whether there was a large spine on the thorax as in 

 IVanncria [pi. 30, fig. 11]. The absence of this information and the 

 conical outline of the anterior lobe of the glabella renders it difficult 

 to make a positive reference of the species to IVanncria. The strong 

 marginal border of the cephalon, small eyes, and the absence of an 

 occipital spine relate it more closely to that genus than to Callavia. 

 It is not improbable that entire specimens will show it to be a form 

 intermediate between Callavia and IVanncria. 



