1896. | NEW YORK ACADEMY OF SCIENCES. 235 
In Agnostus Barrandet, Salter, of the Menevian horizon in 
Wales we evidently have a species of the Levigati section, and 
although Dr. Hicks’ figure* does not show any rim, the descrip- 
tion indicates that there was one; from this and the pygidial 
features this species appears to be allied to A. levigatus, rather 
than A. nudus; but judging from these features, also the two 
individuals figured must at least be of different varieties ; Fig. 
5, if we be guided by the form of the rachis, approaches var. 
forfax, and Fig. 6 var. terranovicus ; the resemblance does not 
establish an identity in either case. 
? AGNostus NuDus, Beyrich. 
This species appears to be indicated by some head shields 
found in Newfoundland. The head shield is high at the back in 
the middle and arched down in all directions, and is devoid of 
marginal fold. 
Sculpture.—Smooth and shining with a minutely punctate sur- 
face. 
Size.—Length and width, 3 mm. 
Horizon and Locality.—Limestone of Chapel Arm, Trinity 
Bay, Newfoundland. 
Micropiscus, Emmons. 
This genus, which in the small number of the pleural joints, is 
almost on a par with Agnostus—for the number varies from two 
to four for the different species—is characterized by certain 
changes of form from its earliest appearance until it died out in 
the later stages of the Paradoxides beds—changes which are com- 
parable to those in Agnostus, but on different lines: one of these 
lines of development is the obliteration of the costz on the side 
lobes of the pygidium, and the other the extraordinary develop- 
ment of the occipital spine. 
The “great nuchal spine” as Salter calls it is not merely an 
extension of the summit of the occipital ring, but in some species 
at least it carries with it the posterior part of the glabella; hence 
these species have no proper occipital furrow, but the two 
outer ends of this furrow are seen to run a little way up the 
side of the spine or form a threadlike band at the the back of 
the spine; in such cases the main furrow seen at the base of 
the spine is in reality the posterior glabellar furrow, and this 
lighter furrow behind is the occipital furrow. 
The obliteration of the occipital furrow in many species of 
this genus leaves one less than the normal number of furrows on 
the axis of the head shield, so that usually not more than three, 
* Quart. Jour. Geol. Soe., London, May ’72, p. 176, pl. V., Figs. 5 and 6. 
