Prof. F. M'Coy on some neiv Lower Palaozoic Mollusca. 189 



reason why tlieir heads arc always directed downwards on such 

 occasions is apparent. 



Epeira diadema and some of its congeners envelope their prey 

 in a sheet of web by the following curious process. Causing 

 tlie victim to rotate by the action of the third pair of legs and 

 the palpi, the first pair of legs also being frequently employed in 

 a similar manner, they extend the spinners laterally, and apply- 

 ing to them alternately the sustentaculum of each posterior leg, 

 they seize and draw out numerous fine lines in the form of a 

 fillet, which they attach to their revolving prey, and thus involve 

 it in a dense covering of silk from one extremity to the other. 

 By means of this stratagem they are capable of overcoming for- 

 midable and powerful insects, such as wasps, bees, and even 

 large beetles. 



In October the female of this species attaches to the inferior 

 surface of stones a subglobose cocoon of yellow silk of a loose 

 texture, measuring §rds of an inch in diameter, in which she de- 

 posits between 700 and 800 spherical eggSaof a yellow colour, 

 agglutinated together in a lenticular form. Withered leaves and 

 bits of dry fern are frequently distributed on the exterior surface 

 of the cocoon. After deserting this nidus, the young spin a few 

 lines on which they group themselves into a compact mass, some- 

 what resembling the granulated fruit of the Rubi. 



XVIII. — Contributions to British Paleontology: — Some new 

 Lower Palcnozoic Mollusca. By F. M'Coy, Professor of Geo- 

 logy and Mineralogy in Queen's College, Belfast. 



Sanguinolites decipiens (M'Coy). 



Desc. Elongate-oblong, dorsal and ventral margins subparallel ; 

 beak incurved, small, depressed, about one-fifth the length 

 from the anterior end ; hinge-line long, not elevated (the in- 

 flected edges forming a nearly horizontal posterior lunette ex- 

 tending its entire length) ; cardinal angle about 115°; anterior 

 end rounded, narrowed by an elongate, elliptic lunette; a strong 

 sigmoidally contorted diagonal ridge extends from the beak 

 to the respiratory angle ; posterior slope steeply inclined ; 

 posterior end slightly oblique, subtruncate, rounded ; ventral 

 margin with a wide, rather deep sinus in the middle, from 

 which a wide concavity extends nearly to the beak, and from 

 the diagonal ridge to the anterior end, which is convex an- 

 terior to the beaks ; surface marked with sharp concentric 

 wrinkles from the anterior lunette to the diagonal ridge- 

 Length 8 lines ; in proportion to the length, greatest width 



