1888.] 



NATURAL SCIENCES OF PHILADELPHIA. 



193 



DESCRIPTIVE NOTES OF NEW AMERICAN SPECIES OF 

 ORB-WEAVING SPIDERS. 



BY HENRY C. MCCOOK, D. D. 

 Epeira gemma, n. sp. 



1. (Fig. 1.) This is one of the largest orbweavers of the Pacific 

 coast, and is found from San Diego northward as far as Victoria, 

 British Columbia. The species varies a good deal in size and mark- 

 ings, but the largest s^dult female (a gravid specimen) measures 



over 20 mm. in length. The abdomen 

 is 15*5 mm. long ; the base of the abdo- 

 men is crowned with two large conical 

 processes. The markings upon the abdo- 

 men are as follows : The forepart which 

 rises quite abruptly from the cephalotho- 

 rax is of a blackish brown color, inter- 

 spersed at irregular periods with yellow 

 spots. Along the median line extends a 

 narrow baud of yellow, upon which are 

 placed two angular or lance head mark- 

 ings, the first of which is j)laced about 

 the middle of the basal part, and the sec- 

 Epeira gemma, female, v 2. o^ifl near the crcst. This baud continues 

 more or less regularly along the dorsum to the apex. About 

 the middle of the dorsum is a shield-shaped figure with scol- 

 loped edges, blackish brown in color for the most part, though in- 

 terrupted by yellow lines of a herring-bone pattern, A narrow 

 yellow border encompasses the shield. The color of the abdomen is 

 yellow, and this color extends to the posterior half of the abdom- 

 inal processes, the anterior half of the same being darkish brown. 

 Dark brown waving and interrupted lines extend along the sides, 

 and between these are small round spots, which are distributed 

 laterally along the sides with more or less regularity. A brownish 

 band extends along the ventral part of the abdomen from the spin- 

 nerets to the epigynum, bordered on either side by a yellowish band 

 and with two short parallel yellowish longitudinal lines drawn equi- 

 distant between these two. 



The epigynum is comparatively small, and between and slightly 

 bent over the dark lateral lobes is a short flat flap ; it is thickened 



