168 MONOGRAM OF THE FOSSIL POLYZOA OF THE 



" The bifurcations occurred at irregular distances, sometimes equalling 3 J lines, and without any pro- 

 minent precursory increase in width ; the branches also exhibited nearly their full dimensions from the 

 very points of divergence, springing upwards after a short curve almost vertically. The portion occupied 

 by the tubular openings formed but a small part of the circumference of the branch ; and when a fragment 

 was placed horizontally ani sideways with the rows of apertures upwards, the latter bore some resemblance 

 to a series of teeth in a maxillary bone. The mouths were generally limited to three in each row, the outer- 

 most being the smallest. The great range of the tubuli explained apparently the considerable dimensions 

 of the reverse portion, the interior of the branches consisting almost wholly of tubes of one character, but 

 decreasing in sides from point to back." 



" The whole of the reverse surface exhibited white longitudinal lines, with interspaces much less in width 

 than the diameter of the tubuli. Their true nature was not ascertained, but it was believed that they were 

 not the walls of the capillary tubes, similar to those which constitute the reverse side of old specimens of 

 Hornera, as they occasionally united, and the interspaces were crossed by irregular filaments. No exterior 

 thickening or change dependent upon age was noticed; and a fixed dorsal surface seen in some species 

 would prevent it is presumed all marked alterations on that side, as it is difficult to conceive that polypes 

 generically identical should possess in certain species a complicated series of vessels, requisite for develop- 

 ing a considerable additional surface, and want it in others." 



" Locality. — Wantoot, South Carolina." [Eocene.] 



We are not acquainted with this nor the following species. 



I. COMMISCENS. 



Idmcmea id., Lonsdale Quart. Jour. Geol. Soc, vol. 1, p. 524, 1845. 

 Crisisina id., d'Orb. Prodrome 2, p. 397. 



"Branches forked, triangular; rows of tubular openings extended nearly to the dorsal surface; no 

 medial ridge or furrow, but an intermingling of mouths; range of tubuli limited; reverse or dorsal sur- 

 face irregular in outline." 



" In the triangular form of the branches, this fossil resembled tbe tertiary species found at Hautville and 

 Grignon, and figured as well as described by De France or Milne-Edwards, under the names of Idmonea 

 gradata and I. ceronopus (De ¥., Atlas Die. Sc. Nat., pi. 45, f. 5. ; Milne-Ed w., Recher. sur .les Polyp., 

 Mem. sur les Ciisie, &c, pp. 24, 23, pi. 12, f. 3,) : but it differed in the central blending of the tubular 

 openings; in this character there was a certain amount of agreement with the recent species of Dr. Milne- 

 Edwards, I. transversa (sp. cit , pi. 9 and 3,) but in the mode of branching, and form of the branches 

 marked differences were presented." 



"The reverse surface indicated apparently the irregular effects of extraneous agency, and not an uni- 

 formity of contour, as in the preceding species. In some fragments the flattening was complete, but the 

 surface was unevenly impressed; in others, though the triangular form was retained, the reverse side was 

 slightly convex, and in one ease partly flat, partly rounded." 



" Locality. — Rock's Bridge." [Eocene.] 



I. Californica, fig. 56. 



Id., Con., Proc. Acad. Nat. Sci. 1855, p. 441. 



Colony composed of dichotomous branches, probably not anastomosing, of variable 



width, often much flattened. Cellules placed on the upper surface in irregular oblique 



lines, obliquity sometimes forwards from the centre, often backwards, at other times 



the direction changes in the same lines, and not unfrequently we find a group of eel- 



