78 ROYAL SOCIETY OF CANADA 



times two or three low tubercles visible. There is also in some specimens 

 a taint trace of a sullicient elevation of the border to indicate an incipient 

 marginal rim." "Locality and jjosition. Station No. 2, North Attle- 

 borough, Mass., Cambrian." 



A peculiar little ti-ilobite which we consider near enough to this to 

 be a mutation, occurs at Manuel's, Conception Bay. 



Mut. viuiLANS, n. mut. (PI. IV., fig. 4a to e.) 



Minute. Only one example and that of the head-shield, known ; 

 this is somewhat angulated in front. No marginal fold is visible, but the 

 wide area in front of the glabella is strongly convex, and is separated 

 from the eye-lobe by a furrow crossing the front of the shield. The 

 conical glabella is depressed in front and much elevated behind, where 

 one pair of furrows is visible, the occipital ring is broken on top but 

 appears to be divided from the glabella by a furrow, and extends back- 

 ward into a spine. The fixed checks are strongly elevated toward the 

 eye-lobe, which is short, convex and very prominent ; there is a tubercle 

 at the root of the ocular fillet which is transverse to the cheek. The 

 posterior marginal furrow is twice as wide at the dorsal suture as at the 

 glabella; the fold is quite narrow, and both arch forward toward the 

 eye-lobe. 



Sculpture. — The surface is not well preserved, as the specimen is a 

 cast of the interior of the test, but it appears to have been tuberculato. 



Size. — Length of the head-shield, 2 mm. ; width of middle piece of 

 the head, 3 mm. 



Horizon and locality. — Calcareous shales (No. 3) of the Protolenus 

 Zone at Manuel's, Conception Bay. 



On comparison with Shaler and Foerste's species above named it will 

 be seen that this has the same size and general form ; the extensions of 

 the dorsal suture approximate to those of that species, they do not go 

 outward, however, but downward, hence it seems possible that the Attle- 

 boro' examples have been flattened ; allowing for this the chief difference 

 in the Newfoundland form is the pear-shaped ocular fillet, the very 

 prominent eye-lobes, the short posterior extension of the dorsal suture, 

 and the forward curve of the posterior mai'ginal fold. 



I think the features of the head-shield in both these forms ally them 

 to Strenuella rather than to Ptychoparia of which no true representatives 

 are known lower down than the Paradoxides beds ; for although the eye- 

 lobe is short it is continuous to the posterior marginal furrow, and so there 

 is no corner of the fixed cheek projecting behind the eye lobe. 



Wo do not suppose this small head to be the larva of S. strenua, 

 because it has the features of a mature shield, e. g. the short prominent 

 eye-lobe and the short conical glabella. It is not Walcott's var. nasuta 



