1911.] NATURAL SCIENCES OF PHILADELPHIA. 173 



The scutum is trapezoidal, the occludent and carinal borders sub- 

 parallel, upper and basal margins about equally oblique; umbo terminal. 

 The tergum is triangular; occludent and carinal margins nearly 

 straight and subequal; occludent margin convex. 



The carina is arcuate, more so in its upper third, the umbo apical, 

 slightly above the middle of the carinal margin of the tergum; roof 

 strongly convex, the plate being U-shaped in section. It widens 

 rapidly towards the base, which enters V-like between the carinal 

 latera. Intraparietes very narrow, bounded by a ridge, and visible 

 only in the upper part of the plate. 



Upper lateral plate trapezoidal with apical umbo; the scutal margin 

 is longest, concave above; the tergal next, arcuate; the carinal and 

 basal margins are straight, equal, and at their junction form a right 

 angle. 



The rostral latera are triangular, obtuse at the rostral angle, widening 

 rapidly to the other end. There is no visible rostrum. 



The inframedian lateral plate is narrow and high, contracting 

 perceptibly at the lower fourth, where the umbo is situated. Carinal 

 lateral plates large, irregular, with the umbo at the lower carinal 

 angle. The carinal margin is concave and longest; basal margin 

 about equal to that opposed to the inframedian latus; upper margin, 

 against the upper latus, and shortest. The two latera meet in a very 

 short suture below the carina. 



The peduncle is extremely short, densely covered with large scales 

 in about 7 vertical rows. 



Length of the capitulum 5, width 2.5 mm. Length of the carina 

 3.75 mm. 



Habitat and Station. — Ten miles south of Key West, Florida, in 

 125 fathoms, on spines of a sea urchin, Dorocidaris , associated with 

 Verruca nexa alba Pils. Types No. 1890, A. N. S. P., collected by John 

 B. Henderson, Jr. 



Numerous specimens taken of nearly uniform size show it to be 

 adult; a view confirmed by the swollen shape of the lower part of 

 the capitulum. It has much in common with S. gracilius Pils., but 

 the rostral latera are quite different in shape, the carina does not 

 extend so high on the terga, the capitulum is less elongate, and the 

 peduncle has more rows of scales. Nearly all other species which 

 are otherwise related differ by having a flat-roofed carina. 



The following were elected members : 

 John Howard McFadden, 

 Edwin S. Stuart, 

 Bayard Long. 



The following were ordered to be printed : 



