Miscidlaneuiis. 237 



Enterobrus elegans, from the mucous membrane of the posterior 

 portion of the rectum of Julus marginatus. 



Remarks. — Since I estabhshed the genus Arthromitus* I have 

 obsers'ed the formation of its sporuli. These originate in the amor- 

 phous matter of the articuh, apparently by a very gradual aggregation 

 and condensation of the contents. They are always single, and 

 usually lie oblique, and frequently alternate with each other in this 

 position in the different articuh. When they first appear they are 

 larger than when fully formed, are frequently bent, or clavate in 

 form, and very indistinct ; but as they ripen, they become more regu- 

 lar, oval, distinct, and quite refractile of light. Usually they are 

 observed at the extremity of the filaments only, but frequently they 

 are found existing in the whole length of the latter. 



A species oi Arthromitus, and also of Cladophytum, is found in the 

 intestine of Polydesmus virginiensis. 



The Higrocrocis intestinalis found by Valentin in the Blatta ori- 

 entalis, I could not find in our domestic cockroach, although I found 

 numerous simple, phytoid, inarticulate filaments, growing from an 

 Oxyuris infesting this animal. — Proceedings of the Academy of Na- 

 tural Sciences of Philadelphia, vol. v. p. 35. 



ON FOSSIL RAIN DROPS. 



Mr. Desor communicated some observations made by Mr. Whitney 

 and himself in reference to the probable origin of the so-called fossil 

 rain drops, which in this country are found on slabs of new red sand- 

 stone, as well as Potsdam sandstone. 



He said it had already been noticed by Mr. Teschemacher that these 

 so-called rain drops, when closely examined, are found to differ in 

 several respects from the impressions made by the rain on a beach, 

 where each drop produces an impression surrounded by a rough crest, 

 more or less elevated according to the force of the rain. The fossil 

 impressions on sandstone, on the contrary, are generally flat and 

 smooth. Besides, there is hardly a shower in which the rain drops 

 are not numerous enough to cover the whole or nearly the whole 

 ground, whereas the fossil impressions are generally scattered and 

 so few in number that it seems almost impossible to ascribe them to 



rain. 



Mr. Desor said, that whilst encamped on the border of Lake Supe- 

 rior, they had several opportunities of studying the action of the waves 

 on the beach during a heavy surf, when they are driven beyond their 

 usual range. It was noticed that when the waves retired from the 

 higher part of the beach, where the slope was less steep, there could 

 be seen several kinds of impressions in the act of forming, some large 

 and flat, others small and deep, (like those which on the sea-shore 

 are generally ascribed to worms or shrimps,) and others likewise deep, 

 but surrounded by a sort of annular, smooth rim. These different 

 kinds of impressions are all produced by the same cause, operating in 

 the same way, namely air-bubbles, which are fonned in the waves of 

 the surf, when rolling over the beach. If an air-bubble becomes 



* Ann. Nat. Hist. Jan. 1850. 



