Stephens — The Frcsh-waler Spovges of Ireland. 237 



The Irisli material of E. Miillcri is obviously too scanty to allow of any 

 study of the variations which may occur in the species. The megaseleres of 

 the Eiver Erne sponge are rather slender ; they measure 0'2-0'25 mm. in 

 length by OOOS-O-dl mm. ; those from the River Tolka specimen are robust, 

 measuring 0'225-0-3 mm. in length by 0013-0'0l8 mm. The amphidises in 

 both cases have a length of 0'01-0-013mm., with a disc 0-02 mm. in diameter. 



Localities. 

 Kf.rky. — C'arauli L., as Spongilla Parfitti '12). 

 Dublin. — E. Tolka near Ashtown. 

 Fermanagh. — E. Erne at Enniskillen (coll. E. Welch). 



Heteromeyenia Ryderi, Potts. 



Ileteromeyenia piciovensis, Potts. 

 Heteromeyenia Maeouni, MacKay. 

 (PI. XXVIII, figs. 2-8.) 



This species was described by Edward Potts in the year 1882 from 

 specimens found in a small stream flowing into the Delaware Eiver, below 

 Philadelphia (29 ). Three years later it was recorded from the State of New 

 Hampshire ; and at about the same time Potts described as new a sponge 

 collected in several lakes in Nova Scotia (32). This sponge he named 

 Heteromeyenia picfovensis. Before long, however, Potts was forced to the 

 conclusion (33, p. 244) that H. pictovensls, as well as other forms he had 

 collected in the meantime, had not sufficient claim to be ranked as distinct 

 species. He accordingly redescribed the typical form of H. Ryderi, adding 

 the following varieties : pictovciisin, Walslii, and Baleni. The species was at 

 this time known in tlio strip of country along the Atlantic coast of North 

 America from Nova Scotia to Florida and in the State of Iowa. Later on it 

 was recorded from Indiana (23). 



In the year 1890 Dr. A. H. MacKay, the discoverer of \he pictovensisioiia 

 of //. Ryderi, described a sponge from Sable Island (26). It grew in 

 abundance in the only fresh-water lake on the island, which is itself merely 

 a great sand-bank twenty miles long by about a mile wide, lying one hundred 

 miles oft' the coast of Nova Scotia. Tiie sponge was considered to be a distinct 

 species, and was named //. Macmmi. At the same time, the author noticed 

 its likeness to certain forms of H. Ryderi, with slender spicules, and suggested 

 that it might have to be reduced to a variety of that species. From an 

 examination of some of the type material kindly given me by Dr. MacKay, 

 I have come to the conclusion that the Sable Island sponge cannot be- 

 separated specitically from H. Ryderi. It is, indeed, exactly similar to 



B.I. A. PROC, VOL. XXXV, SECT. B. [2 .0] 



