THE MOUNT DESERT REGION 



99 



viduals. Developmental forms of both the large and small 

 anisochelae were abundant in all stages of development. 



Remarks: Mycale ovuliim is distinguished by the absence 

 of sigmata from Mycale lingua. 



From the Gulf of St. Lawrence Lambe has described as 

 Esperella modesta a form which Lundbeck considers to be 

 very probably identical with Mycale ovulwn. 



Geographical distribution. Davis Strait (Lundbeck) ; Gulf 

 of St. Lawrence {Esperella modesta, Lambe) ; Mount Desert 



Region. 



Myxilla 0. Schmidt 

 MyxhjLA incrustans (Johnston) 



Lundbeck (1905, p. 132, pi. 4, figs. 6, 7; pi. 14, fig. 3a-h). 

 This species was taken at Shore Station 4, encrusting a 

 Modiolus, near low water. 



Skeleton. This is chiefly a polyspicular reticulation of 

 triangular meshes, although it may be quite irregular and 

 more diifuse. 



Spicules. Megascleres are straight or slightly curved 

 spined styli with the head end sw-ollen (tylostyli) and more 

 heavily spined than the shaft of the spicule. 



Frequently the curve in the spicule is displacd toward the 

 head end. These spicules vary in length from .145 mm. to 

 .243 mm., with the mode at .203 mm. 



The tornota are straight or curved ^\^th the bend occurring, 

 sometimes abruptly, at almost any point on the shaft. In 

 the majority of these the ends are minutely spined and dis- 

 similar; one end is more bulbous than the other, which is 

 elongately oval in shape. These spicules vary in length from 

 .162 mm. to .203 mm., with a modal length of .186 mm. 



Microscleres are isochelae of two sizes and sigmata. The 

 large isochelae are tridentate and vary in length from .037 

 mm. to .05 mm., with the mode at .043 mm. The small iso- 

 chelae vary in length from .018 mm. to .026 mm., and, in this 

 specimen, they are not so abundant as the large isochelae. 



Simple and contort sigmata are present in great abundance 

 and vary from .024 mm. to .037 mm., with a modal length of 

 .028 mm. 



