168 SYNOPSIS OF THE CHARACTERS OF THE 



others ; it most closely resembles the C. inornata, M'Coy, but is more gibbous, and has more nearly equal ends. 

 Length about one-third of a line. 



Cythere scutulum. {M'Coy. (PL XXIII. fig. 21 ). 



Sp. Ch. — Orbicular, compressed, smooth; sides flat; ventral margin about one-third the length of the 

 shell ; the ends equal, projecting below the ventral margin. 



This species approaches the C. orbicularis, M'Coy, in shape, but is well distinguished by the form of its 

 ventral margin, and the perfect flatness of its sides, the sides of C. orbicularis, M'Coy, being very gibbous or 

 obtusely conical. Length one line. 



Cythere spiNiGEKA. M'Coy. (PL XXIII. fig. 23). 



Sp. CA.— Shell somewhat reniform, sides slightly concave; one spiniform tubercle close to the end on each 

 valve ; a slight abdominal sinvis. 



This species has both ends alike, and the sides a little concave ; there is a very small abdominal sinus, 

 while the back is much and regularly curved ; tlie portion of the valve which overlaps is much thickened ; in 

 this species the two tubercles are entirely beyond this portion, while in C. cornuta, they are nearly in the 

 centre. Length from one line to a hne and a quarter; diameter two-thirds the depth; depth two-thirds the 

 length. 



Cythere tritubercitlata. M'Coy. (PL XXIII. fig. 24). 



Sp. Ch. — Oblong, length rather more than twice the depth, convex ; both ends equal, rounded ; dorsal 

 and ventral margins nearly parallel, each valve Avith three small, round, nearly equidistant tubercles, one of 

 which is much closer to the ventral margin than the other two. 



This species, in addition to its lengthened, regular form, is easily distinguished from its congeners by the 

 three tubercles on each valve. Length half a line. 



ANNELIDA. 



The Annelida, or red-blooded worms, are the least highly organized group of the Annulosa, or articulated 

 animals ; the forms found in the carb. limestone belong to Cuvler's order Tubicola, or those sedentary species 

 having the gills attached to the head, and inhabiting a tube, sometimes shelly, as in Serpula, sometimes nearly 

 membranous, or formed of agglutinated grains of sand, as in Terebella or Sabella. 



Serpxjla. Linn. 

 Gen. Ch. — Tubular, gradually widening towards the aperture ; irregularly attached ; aperture round ; edge 

 simple. 



Serpula (?) coMPRESSA. Sow. 



Serpula compressa. Sow. Min. Con. 



Sp. Ch. — Tube thick, perlaceous (?) rapidly tapering, flexuous; section elliptical. 



The examples I have seen of this species seem more allied to Serpulites than to Serpula : the pearly or 

 glistening appearance of the surface more nearly resembling the former than the latter genus. Diameter four 

 lines. 



