1887.] NATURAL SCIENCES OF PHILADELPHIA. 233 



This species is a very interesting one, furnisliing the first instance 

 among fresh-Avater sponges, in which the dermal spicule, generally 

 a slender, smooth or more or less spiniferous acerate, is here seen as 

 a well defined and symmetrical birotulate. Mr. Carter has kindly 

 brought to my notice a very similar spi'cule occupying a like position 

 in the marine form Halichondria hirotulata, Higgins, from the West 

 Indies and S. Australia ; but in the case of those from fresh-waters, 

 we have had nothing more definite than the immature or apocryphal 

 forms in M. crater if ormis. The very peculiar dermal spicules char- 

 acterizing M. plumosa are most suggestive of this, or possibly, of a 

 still more advanced type. {Spongilla boJimii and S. novce terrce, were 

 discovered later.) 



The re-discovery of this species among the magnificent collections 

 of sponges made by Mr. MacKay from the water-shed and other 

 lakes abounding in Pictou County, Nova Scotia, gave me great 

 pleasure, as showing the persistence of the type in widely separated 

 districts ; and for the confirmation it afibrded of my previous obser- 

 vation, as to the general strengthening of spicular features in sponges 

 as their localities approach sea-level. 



(17) Meyenia plumosa, Carter; (Spongilla Jilumosa, Carter.) Ann. and 

 Mag. Nat. Hist. 1849, p. 81. 



"Massive, lobate. Structure feathery, fibrous, friable. Color 

 greenish or light-bi'own. Skeleton-spicule curved, fusiform, grad- 

 ually sharp-pointed, smooth. Flesh-spicule stelliform, consisting of 

 a variable number of arms of various lengths radiating from a 

 large, smooth globular body ; arms spined throughout ; spines long- 

 est at the ends, so as to present a capitate appearance, and recurved 

 generally ; the whole varying from a simple, spinous linear spicule 

 to' the stellate form first mentioned, thus modified by the size and 

 presence of the globular inflation and number of arms developed 

 from the centre of the former ; abundant in all parts of the struct- 

 ure, but especially in the neighborhood of the statoblasts. Stato- 

 blast ellipsoidal ; aperture lateral, infundibular ; crust, which is 

 thick and composed of granular microcell-substance, charged with 

 birotulate spicules consisting of a long, straight, sparsely spiniferous 

 shaft whose spines are large, conical and perpendicular, terminated 

 at each end by an umbonate disk of equal size, whose margin is ir- 

 regularly denticulated, with the processes more or less turned in- 

 wards, arranged perpendicularly, with one disk resting on the chiti- 



16 



