The Invertebrate Animals of the Miocene period are very numerous, but they belong for the most part to existing types, and they can only receive scanty consideration here.  The little shells of Foraminifera are extremely abundant in some beds, the genera being in many cases such as now flourish abundantly in our seas.  The principal forms belong to the genera Textularia (fig. 237), Robulina, Glandulina, Polystomella, Amplistegina, &c.  Corals are very abundant, in many instances forming regular “reefs;” but all the more important groups are in existence at the present day.  The Red Coral (Corallium), so largely sought after as an ornamental material, appears for the first time in deposits of this age.  Amongst the Echinoderms, we meet with Heart-Urchins (Spatangus), Cake-Urchins (Scutella; fig. 238), and various other forms, the majority of which are closely allied to forms now in existence.

[Illustration:  Fig. 237.—­Textularia Meyeriana, greatly enlarged.  Miocene Tertiary.]

Numerous Crabs and Lobsters represent the Crustacea; but the most important of the Miocene Articulate Animals are the Insects.  Of these, more than thirteen hundred species have been determined by Dr Heer from the Miocene strata of Switzerland alone.  They include almost all the existing orders of insects, such as numerous and varied forms of Beetles (Coleoptera), Forest-bugs (Hemiptera), Ants (Hymenoptera), Flies (Diptera), Termites and Dragon-flies (Neuroptera), Grasshoppers (Orthoptera), and Butterflies (Lepidoptera).  One of the latter, the well-known Vanessa Pluto of the Brown Coals of Croatia, even exhibits the pattern of the wing, and to some extent its original coloration; whilst the more durably-constructed insects are often in a state of exquisite preservation.

[Illustration:  Fig. 238.—­Different views of Scutella subrotunda, a Miocene “Cake-Urchin” from the south of France.]

The Mollusca of the Miocene period are very numerous, but call for little special comment.  Upon the whole, they are generically very similar to the Shell-fish of the present day; whilst, as before stated, from fifteen to thirty per cent of the species are identical with those now in existence.  So far as the European area is concerned, the Molluscs indicate a decidedly hotter climate than the present one, though they have not such a distinctly tropical character as is the case with the Eocene shells.  Thus we meet with many Cones, Volutes, Cowries, Olive-shells, Fig-shells, and the like, which are decidedly indicative of a high temperature of the sea. Polyzoans are abundant, and often attain considerable dimensions; whilst Brachiopods, on the other hand, are few in number.  Bivalves and Univalves are extremely plentiful; and we meet here with the shells of Winged-Snails (Pteropods), belonging to such existing genera as Hyalea (fig. 239) and Cleodora.  Lastly, the Cephalopods are represented both by the chambered shells of Nautili and by the internal skeletons of Cuttle-fishes (Spirulirostra.)