REPORT OF THE DIRECTOR I918 213 



sickle-shaped, thin walled (originally hollow) process from the middle 

 of the third ( ?) joint of the first pair of endognathites. It is the first 

 time, to my knowledge, that this organ has been observed in any 

 American eurypterid. Holm had before repognized this hcckhke 

 appendage inEurypterus fischeri, where it is attached to 

 the fifth segment of the second endognathite (see Clarke and Ruede- 

 mann, p. 157), and by analogy with Limulus, considered it as a clasp- 

 ing organ. 



Hughmilleria phelpsae nov. 



Plate 3, figures 1-3 



The Vernon shale has furnished two specimens of a Hughmilleria 

 that proved distinct from H. socialis Sarle of the underlying 

 Pittsford shale. 



The specimens consist only of carapaces, attached to which are 

 several of the anterior tergites and in one case also the operculum 

 and female opercular appendage. We shall therefore merely point 

 out the differences from the completely known H. socialis that 

 are apparent in these fragments. 



The carapace is relatively broader and shorter in this species; 

 while in H. socialis length and width are about equal, the width 

 is here greater by one-fifth to one-fourth. In the type (plate 3, 

 figure 2), the width is 10 mm, but the length only 8 mm. In the 

 other larger specimen, the two dimensions are 18 mm and 13 mm 

 respectively. 



The compound eyes are not marginal as in H. socialis but 

 distant from the margin about one-half the length of the eye. 



The surface sculpture consists on the carapace of five parallel lines 

 along the frontal margin, irregularly distributed, small tubercles on 

 the posterior portion of the carapace and a fringe of fine triangular 

 scales along the posterior margin. The tergites bear three to four 

 parallel lines along the posterior margin, which posteriorly are 

 followed by five scalloped lines which finally break up into series of 

 faint, separate, lunate scales. In the larger specimen there are seen 

 near the posterior margin of the second tergite traces of larger prom- 

 inent triangular scales. The operculum bears imbricating angular 

 scales asinH. socialis. 



The opercular appendage is longer than that ofH. socialis and 

 posteriorly expanded. Likewise is the appendage of the following 

 sternite expanded at its extremity. 



While H. phelpsae is clearly distinct from H. socialis 

 n the characters here pointed out, it has these in common with 



