308 NEW YORK STATE MUSEUM 



in the absence of these there must be some reservation made, 

 subject to future demonstration or correction. 



Hughmilleria shawangunk nov. 



Plate 4, figures 1-4; plate 5, figures i-q 



With the same form of head and outline of body as in 

 H. s o c i a 1 i s this species combines a diminutive size, the aver- 

 age being well shown in figures I and 3 of plate 4. The full equip- 

 ment of abdominal segments (12 and telson) is possessed at this 

 adult stage. 



Exceedingly instructive but of the same tenor as evidence already 

 given are the developmental stages. On plate 4, figure 2 is repre- 

 sented under great enlargement from a camera drawing an entire 

 individual 2.5 mm in actual length, the smallest known of the 

 fossil merostomes. This is in no sense a nauplius and we are 

 entirely without evidence of any such stage in these crustaceans. 

 It is however an emphatic expression of . the differences between 

 the nepionic condition and the adult, showing the short, broadly 

 triangular head, the expanded abdomen which under the best 

 illumination appears to carry but five segments and the abruptly 

 contracted postabdomen with five narrow and deep segments. Thus 

 again in this very early growth stage is the scorpioid outline sharply 

 defined. On consulting the figures of various head shields of dif- 

 ferent sizes shown on plate 5, it will be seen that there is not much 

 variation in the position of the eyes. In some instances the eyes 

 are not discernible [fig. 5, 6] . and it is quite possible that in these 

 they may be still entirely submarginal. 



Genus pterygotus 

 Pterygotus ? otisius nov. 



Plate 6, figure 7 



An elongate subquadrate head with eyes anterior, far apart and 

 just within the margins ; ocellar mound well back between the 

 posterior horns of the eye crescents ; surface quite smooth. The 

 specimen figured and one other of similar character are all that is 

 known of this species. 



Genus stylonurus 



Stylonurus ? sp. 



Plate 6 , figures 9 ( ?) , 1 o ( ?) , 1 1 , 1 2 ; plate 7 .figures 1-5 ; plate 8 , figures 9 , n (?) 



Everywhere through these dark shales are fragments of large 

 crustaceans most of which are so distorted as to no longer show 

 the outline of the parts though they exhibit distinctive surface 



