54 NEW YORK STATE MUSEUM 



through the translucent crust of a pygidium of Phacops 

 cristata var . p i p a - 1 



Hall and Clarke consider the pits to be " areas of insertion for 

 somitic muscles, the marginal pair probably connected with the 

 natatory appendages, the axial pair possibly attached to the 

 branchial apparatus, or to the viscera. The function of the 

 median pits upon alternate grooves is not understood." On the 

 upper surface of the crust of the Devonic species no indications 

 of these characters were found. The axis of the pygidium of 

 Ampyx is usually perfectly smooth or only provided with two 

 or three faint annulations on the anterior part. One species, how- 

 ever (pi. 3, fig. 10) possesses a broad elevation along the median 

 line of the axis; the indications of annulations, which in this 

 species extend well toward the posterior end of the axis, are more 

 distinct on the sides of the axis, than on the median elevation; 

 the extent of this elevation, falling approximately in the region 

 without distinct muscle scars, and the more distinct annulations 

 on the sides, which probably are caused by the presence of the 

 muscle scars, are indications of the influence of the strain 

 exerted by the muscles on the configuration of the external crust. 



REMOPLEURIDES Portlock 



Subgenus remopleurides s. str. 



Remopleurides tumidus sp. nov. 

 PI. 4, fig. 2-4 



Two cranidia found in a pebble of dark gray, reddish 

 weathering limestone (oistracode bed) differ so materially 

 from the next described, Remopleurides linguatus, 

 a form of most profuse occurrence in the black compact limestone 

 pebbles, that they can not be considered to represent merely a 

 later growth stage of the more common smaller species, but evi- 

 dently represent a different type. 



Diagnosis. Cranidium broadly elliptic, longest diameter at the 

 posterior third; the longer diameter to the shorter as 10:9, poste- 



1 Pal. N. Y. 1S88. v. 7, pi. 8 A, fig. 15. 



