16 



time by Dr. Wood, of Portland. After our specimen was 

 stuffed and dried, it proved to be the Somniosushi^evipinna, 

 Lesueur. Lesueur described his fish from a dried and 

 stuffed skin, which he saw in Marblehead, in 1818. Our 

 fish, when recent, did not answer at all to that description or 

 figure ; but when stuffed and dried, it agreed with it per- 

 fectly. One characteristic in particular worthy of notice, 

 the lateral line, scarcely observable in the recent fish, is ex- 

 ceedingly well marked, exhibiting the vertical bands pointed 

 out by Lesueur. These three specimens, Lesueur's, Dr. 

 Wood's, and the one belonging to the Society, are all the 

 Somniosus brevipinna, the Nurse or Sleeper Shark. 



Prof. Rogers made some remarks upon the Infusorial de- 

 posit at the mouths of rivers in the Southern States. On the 

 Rappahannock, York, and James rivers, these deposits are 

 in great development. They are caused by the influx of 

 vast numbers of marine Infusoria by the flood-tide, which, 

 on meeting the fresh water of the river, are instantly de- 

 prived of life, and sink, leaving their silicious or calcareous 

 covering to swell the mass of delta and raise the river bed. 



Dr. Goald remarked, that not only do the Marine animalculse 

 perish on meeting the fresh water, but tribes of fresh water 

 species also are destroyed by the access of the water of the 

 ocean, and add their bodies to swell the general mass. 



Mr. Desor presented some remarks on some peculiar bo- 

 dies which are seen moving in the interior of the eggs of 

 different kinds of Eolis, and which have been described by 

 M. Nordmann as parasites, under the name of Cosmella hy- 

 drachnoides. 



They are small spheres, with long, transparent threads attach- 

 ed to them, by means of which, with undulations like those of a 

 whip-lash, they move about with great activity. Some observers 

 might be led to consider them as independent existences. One 

 might even suppose them to be the first stale of those peculiar 

 parasites which Dr. Gould has found so numerous on the append- 

 ages of the full-grown Eolis. But, on the other hand, when we 



