106 THE CRAG POLYZOA. 



smooth, and finely streaked. One or two of the species of Idmonea figured under various 

 generic names by D'Orbigny, might be thought to resemble I.fenestrata, but it seems 

 scarcely worth while to discuss these similarities. 



3. I. DELICATULA {ll. sp.) PI. XV, fig. 8. 



Polyzoario ramoso ; ramis gracilibus furcatis, postice rotundatis, antice subangulatis, 

 Cellulis 5 — 6 singulis in seriebus; seriebus subaltern antibus non raro oppositis, mediaque 

 in linea conjunctis. Superficie anteriori cellularum convexa, minutissime punctulata. 



Polyzoarium composed of slender forked branches, rounded behind, subangular in 

 front ; cells 5 or 6 in each series ; series subalternate, often opposite and meeting in the 

 median line ; front of cell convex, very finely dotted ; dorsal surface of branches smooth, 

 striated, dotted. 



Habitat. — C. Crag, Sutton, S. Wood. 



Owing apparently to the extreme thinness and fragility of their walls the openings of the 

 cells in nearly every specimen of this most abundant species are so much worn away, that in 

 fact the whole front of the cell is usually laid open, so that the surface presents a sulcate 

 aspect — the sulci being interrupted at each successive series of cells. The dorsal surface 

 when entire is quite smooth, and marked only by parallel longitudinal lines indicating the 

 walls of minute elongated tubules ; and owing to the delicacy of their walls these tubules, 

 like the cells, are in many cases laid open, consequently in the majority of specimens the 

 dorsal surface exhibits a finely sulcated appearance. 



4. I. INTRICARIA [71. Sp.) PL XV. fig. 7. 



Polyzoario e ramis cylindricis confuse intertextisetirregulariter conjunctis, e pedunculo 

 communi basi dilatato surgentibus, composito. Cellularum orificiis in seriebus lateralibus, 

 irregularibus, obliquis dispositis, non raro etiam sparsis. Superficie anteriori subconvexa, 

 punctulata, glabra ; posteriori glabra, lineis reticulatis signata, punctulata. 



Polyzoarium composed of intricately interlaced and anastomosing subcylindrical 

 branches, springing from a common peduncle, which is expanded at the base ; openings of 

 cells in irregular, oblique, lateral series, and often scattered ; anterior surface subconvex, 

 dotted, even ; dorsal smooth, marked with anastomosing lines, dotted. 



Habitat. — Cor. Crag, Sutton, 8. Wood. 



The usually scattered or irregular disposition of the mouths of the cells gives fragments of 

 this species, in many cases, the aspect, so far as that goes, of a Hortiera. In other parts, 

 however, the distinct serial arrangement of the openings on the sides of a branch, and the 



