6s2 



SCIENTIFIC NEWS. 



[Dec. 28, iE 



the new British species Cymbasoma Herdmani, I.C.T. 

 The form about to be described was, however, the 

 earliest found, and the writer has since also found it in 

 the Maltese seas. Its length is about £ inch. The first 

 joint of the cephalothorax (fig. 1) is equal in length to 

 the succeeding five, the last being much smaller than 

 the others, and appearing as though part of the abdo- 

 men. The eyes are long and kidney-shaped, with a con- 

 spicuous brain below. The anterior antenna? (fig. 2) are 

 about eight times as long as the broadest part, and ter- 

 minated by two claw-like spines; the inner side of each 

 antenna has five hooked spines (fig. 2). From two 

 raised circumferences near the centre proceed long 

 spinous setae, and several smaller setae are situated near 

 the apical portion of the antennae. The first four pairs 

 of swimming feet (fig. 3) have strong muscular basal 

 joints, from which proceed two 3-jointed branches, with 

 thick terminal setae. The fifth pair of feet are each 

 composed of a long joint, at the apex of which are three 

 strong spinous setae. The abdomen is very muscular; 

 the caudal setae are short, broad, and divergent, and are 

 each terminated by three strong setae. 



One specimen only, a female, was taken in the tow-net, 

 at Orotava, Teneriffe. 



The lower portion of the body is of a deep sepia 

 colour. The animal is peculiarly rigid and muscular. 



The illustrations accompanying the paper are taken 

 from Mr. Thompson's drawings in the Transactions of the 

 Liverpool Biological Society and the Linnaean Society 

 of London. 



THE GEOLOGICAL HISTORY OF 

 SHARKS. 



TN the Suffolk Crag great numbers of sharks' teeth 

 occur, and among these are many of large size, 

 which bear the name of Carcharodon. They are often 

 upwards of four inches in length, triangular in outline, 

 and armed along the cutting edges with close-set toothlets, 

 such as are so often found upon the large knife-like teeth of 

 carnivorous animals. The great sabre-toothed feline 

 (Machairodus) of our late tertiary times, and the extinct 

 carnivorous reptile Dicynodon of South Africa are well- 

 known instances of the same thing. It is plain that a tooth 

 so armed lacerates the flesh more extensively and com- 

 pletely, penetrates further, and is more easily withdrawn. 

 A knife-blade passed into soft wood, or cheese, or flesh, 

 soon jams, and can hardly be moved backwards or for- 

 wards ; but if the edges are furnished with saw-teeth, 

 the tool enlarges its cut, and will penetrate much deeper. 

 Teeth of the Carcharodon occur also in the tertiary 

 deposits of Florida and Carolina. In some places they 

 are so plentiful that ship-loads are regularly sent to 

 England for conversion into super-phosphates, the same 

 process being, as our readers well know, applied to the 

 fossil bones and teeth of the Suffolk Crag. Many of 

 these fossil teeth were dredged up from the bottom cf 

 the Pacific during the expedition of the Challenger. A 

 closely-allied species {Carcharodon Rondclelii) still sur- 

 vives in the seas of warm climates. It attains the great 

 length of forty feet, but the tertiary shark of the same 

 genus must have exceeded even this enormous bulk. 

 The recent and fossil teeth hardly differ materially, but 

 of course there may have been more conspicuous differ- 

 ences in the perishable parts of the body, with which we 

 cannot hope to become fully acquainted. 



Agassiz and other palaeontologists have described 



many kinds of large crushing teeth borne upon the jaws 

 of very ancient sharks. Some are known from the 

 Devonian formation. A vast number of forms have 

 been figured from the limestones of the Carboniferous 

 period, and the succession lasts, with hardly diminished 

 numbers, down to the Lias, after which there is a great 

 falling off in the variety and frequency of these fossils. 

 The key to the arrangement and use of such teeth has 

 been found in the recent Cestracion Philippi of Port 

 Jackson, a shark whose fore teeth are pointed and 

 adapted to the seizing of prey, while the hind ones form 

 a tessellated pavement, set with regular rows of large 

 and powerful grinders, which are rendered intensely 

 hard by the dense enamel which covers the exposed 

 surface, and yet to some extent movable by reason of 

 the membranous spaces between. This dentition is well 

 suited to the crushing of Crustacea and hard-shelled 

 mollusks. 



Among the oldest sharks are some whose teeth were 

 subdivided into several long-pointed cusps, smaller ones 

 sometimes intervening. These belong to the extinct 

 genus Cladodus, which is first met with in Devonian 

 rocks. Quite recently Garman has described a very 

 peculiar deep-sea shark from Japan, to which he gives 

 the rather repellent name of Chlamydoselaclnts anguineus. 

 It has an unusually long but nevertheless shark-like 

 bodj', a wide mouth opening quite at the fore end of 

 the head, as in most fishes, and not beneath, as is usually 

 the case with sharks. The gill-openings are extremely 

 wide in comparison with any other shark. The teeth 

 closely resemble some of those attributed to Cladodus, 

 and good naturalists could be named who maintain that 

 the old Devonian fish still survives in the Japan seas. 

 Others believe that the form of the teeth in sharks 

 cannot possibly justify a confident assertion of identity, 

 but there can be little doubt as to the near affinity at 

 least of the creatures separated by so vast an interval of 

 time. 



The oldest known sharks are also among the oldest 

 known vertebrates. They are represented by teeth, 

 scales, and possibly spines found in the bone-bed of the 

 Ludlow formation (Upper Silurian). Some long extinct 

 fishes (Pleraspis) claim an equal antiquity, but no sur- 

 viving form of vertebrate life can be traced back anything 

 like so far as the family of sharks. 



Upon this remarkable persistence of an extremely 

 ancient type we have to make two remarks. Firstly, 

 that it is in singular conflict with the general course of life 

 upon the earth. In seas, as in wide continental areas, 

 there is a profusion of competing forms ; new races 

 appear frequently, and spread fast; ancient types are 

 suppressed, or driven out into secluded regions. We 

 find that the truly ancient families among animals are 

 now to be sought chiefly in ponds and lakes and rivers, 

 even such as once could hold their own in the broad ocean. 

 But the tide of time has not exterminated the sharks, 

 nor even compelled them to take refuge in corners. They 

 are still numerous, varied and widespread — truly a 

 dominant race, notwithstanding the lapse of uncounted 

 ages. 



In the second place it is not a little startling to find in 

 sharks rudiments and embryonic structures, not service- 

 able to the animals themselves, though immensely 

 interesting to the naturalist, who learns thereby some- 

 thing about their yet more primitive pre-Silurian and 

 invertebrate progenitors. The external gills, which never 

 serve to aerate the blood, and the early stages of the 



