TURBINAEIA. 15 



1. Cratenform Type. — This applies to all those Turbinarians -which retain for a long time 

 the cup form, but slightly modified. In the present state of our knowledge, it is impossible 

 to say whether this is a natural group. Certain it is, liowever, that some Turbinarians grow 

 to an enormous size as simple cups. When, therefore, we consider the improbability of the 

 budding of the radial polyps persisting uniform round an ever-enlarging circxunference, which 

 is the only way in which the cup can retain its early symmetry, we feel bound to accept these 

 large cups as definite specific growths, and not mere sports (Plate I.). 



I propose, also, to include in this group such forms as T. Dance, in which the cup shape, 

 though modified, is always recognisable (Plates II.-V.). 



This group is also useful as a temporary resting-place for the young cups which cannot 

 be associated with any known species, it being understood that the discovery of their adult 

 stages (adult meaning that stage which reveals the definitive type of growth) may compel us 

 to transfer them to other groups (Plate VI.). 



2. PcUiforni Type. — This term, again, properly applies only to the early shield-like 

 modification of the cup. The subsequent growth of this shield may vary greatly. The 

 variations depend upon whether the early form is convex or concave. The convex specimens 

 may form great hemispherical masses. Slightly concave forms may persist as such, the sur- 

 face throwing up huge flat and branching staghorn-like processes ; while the more concave 

 forms may show most of the tyj^ical methods of growth of young cups. It is worth noting 

 that the uncertainty of the subsequent growth of peltate young forms appears to be due to 

 the fact that this shape is, as it were, upon the border-line between concave and convex 

 (Plates VII.-IX.). 



3. Frondcns Type. — This group is intended to include forms in which the erect margin of 

 the bowl-shaped cup is compelled by growth to break up into lobes, which curl round more or 

 less vertical axes — the " cucuUate infolding " of Dana (Plates X. and XI.). 



4. Foliate Type. — This group is intended to comprise forms in wliich the margin of the 

 cup continues as a complicated mass of intertwining, wavy, more or less erect fronds, which 

 fuse irregularly with one another (Plates XI.-XV.). 



5. Mcscntcriform Type. — This includes those forms in which the margin forms open 

 frills, which are left behind by the growing edge as cylinders. The growing edge appears 

 lobed between the cylinders. The.ie marginal lobes grow out horizontally, periodically bend 

 upwards, curl round, continually forming new, more or less erect cylinders or finger-shaped 

 processes (Plates XV. and XVI.). 



6. Tahulatc Type. — The coralla in this group form horizontal, dish-like gro^^"ths. Each 

 fresh growth covers the previous with a larger and thicker dish, there being often a space or 

 fissure left between the two growths (Plates XVII.-XX.). 



7. Glomerate Type. — The corallum thickens enormously in the centre, by the lengthening 

 of the polyps, while tiie margin hangs down. Each new growth creeps over the one which 

 preceded it. 



The specimens in the Collection do not supply us with any direct proof that these 



