Sept. 1, 1S69.] 



HARDWICKE'S SCIENCE-GOSSIP. 



195 



Many fables have been written about it ; the 

 ancients supposed that in return for cheap lodg- 

 ings it acted as a watch-dog, keeping a sharp look- 

 out and warning its eyeless host of coming danger: 

 with this idea Aristotle named it Ilivv6<pv\a£, the 

 Pinna's guard. 



Almost buried beneath the roots, and cemented 

 to the stone on which the roots have laid hold, is a 

 thin, delicate, and translucent but poisonous mem- 

 ber of the oyster tribe, an A/wmia (dvdfioiog, unlike); 

 so called from its two' valves being totally different 

 from each other in shape and size. The left or upper 

 valve is convex and full, while the right or lower is 

 scarcely one half as large, and is concave and bent 

 about to adapt itself to the foreign body to which 

 it is attached. In the lower valve near the hinge is 

 an orifice, through which a byssus-like muscular 

 band tipped with a shelly button or plug (concern- 

 • ing which the learned have had many disputes) 

 passes, by which the creature effects its hold : it is 

 often seen encrusted on the common oyster, and we 

 rarely examine a root of Lamiiiaria without finding 

 a specimen : it is often called the Saddle Oyster ; 

 its lawful name is Anomia Ephippium. 



Twisted amongst the roots are some limp unplea- 

 sant-looking flattened tubes four or five inches long, 

 like slips of wet whity-brown paper powdered with 

 sand. Put them into the bottle of salt water ; they 

 contain the pretty annelids Eunice tubicola (of 

 Cuvier) ; we must examine them at home. We can- 

 not pause to overhaul the seaweeds any longer, but 

 let us roll back a yard or two of this mass, and see 

 if there is anything under them. 



Fig. 137. The Sandhopper {Talitrus locusta), x 5. 



The very ground seems to be alive. First of all let 

 us secure a dozen or two of these Sandhoppers, 

 Talitri, crustaceans of the order Amphipoda : these, 

 in consequence of their jumping propensities, are 

 distinguished by the title Amphipoda saltatoria. 

 To economize space and to avoid repetition, we 

 must refer our readers to the April number of this 

 present year, in which, under the head of Fhronima, 

 will be found suudry details respecting crustaceans 

 in general and Amphipods in particular. 



The genus Talitrus, of the family Orchestiidce, 



display the following characteristics, according to 

 Messrs. Bate and Westwood, from whose great 

 work on " The British Sessile-eyed Crustacea " the 

 above and the three following figures are taken : — 

 " Superior antennae short and rudimentary. In- 

 ferior antennae with the basal joints fused into the 

 facial wall of the cephalon. Mandibular palpi ob- 

 solete. Maxillipedes not unguiculate. First pair 

 of gnathopoda simple ; second pair small and feeble. 

 Coxae of third pair of pereiopoda as deep as the 

 coxae of the second, and divided into two equal 

 lobes. Telson rudimentary;" and the specific 

 character of T. locusta. " Superior antennae only 

 reaching to half the length of the penultimate joint 

 of the peduncle of the lower. Last joint of the 

 peduncle of the inferior antennae nearly twice as 

 long as the penultimate. Eirst pair of gnathopoda 

 robust and powerful. Second pair feeble, mem- 

 branaceous, terminating in an imperfectly formed 

 subchelate band : dactylos small and remote from 

 the extremity of the propodos. Posterior pair of 

 pleopoda very short. Telson rudimentary. Length 

 half to three-quarters of an inch." 



The first we catch is one of the above-described 

 Sandhoppers (T. locusta), by far the commonest 

 and most abundant members of the family Orches- 

 tiidce. They are said seldom to enter the water 

 voluntarily, but to dwell under the seaweeds at the 

 top of high-water mark, or to burrow in the sand. 

 We have found them in myriads in the cracks in 

 the clay on the face of the cliffs, or high banks 

 between Brown-down and Hill-head, at least three 

 feet above the highest part of the beach. Although 

 of a purely aquatic character, and re- 

 quiring constant moisture, they die if kept 

 long in water : they are carnivorous, and 

 highly useful as scavengers ; they have no 

 objection to turn cannibals and eat each 

 other ; thus assisting the gulls and plovers 

 in keeping down the undue multiplication 

 of their legions. The French have named 

 them Puces de Mer : the name given 

 them, in allusion to the peculiar motion 

 of then; tail in [leaping, is from the Latin 

 talitrum (a flip or fillip). 



The genus Orchestia present the general 



appearance of Talitrus, but have both pairs 



of gnathopods subchelate ; the second pair 



in the male large and powerful ; in the female, small 



and feeble ; the telson single and well developed. 



Specific character : — " Second pair of gnathopoda 

 having the propodos tapering, the palm occupying 

 nearly the entire length of the inferior margin, 

 defined by a large tooth at the inferior angle." This 

 species of the genus Orchestia (fig. 138) seems to be 

 found chiefly on the coasts of Devon and Cornwall, 

 where another genus, Allorchestes, is also found: 

 we have not met with them here. For fuller details, 

 and for drawings and descriptions of all the known 



k 2 



