3348 THE MOLLUSKS OR SHELLFISH 



and mud in search of bivalves. The operculum is often somewhat triangular, with 

 fine serrations along the sides. N, reticulata, the largest of the British species, is 

 common all round the coast. It is a great nuisance on oyster beds, and although 

 exhibiting a preference for young oysters, also attacks those of more mature growth. 

 The egg capsules are roundish, very compressed, and attached by a short stalk to 

 seaweeds. They are arranged close together in compact series, and have a small 

 hole at the top, through which the young escape. The subgenus Demoulia resembles 

 Nassa as regards the shell, but the animal (of D. retusa at all events) has no 

 prolongations at the posterior end of the foot. The operculum is present in some 

 species, wanting in others. Four of the seven known species are from West and 

 South Africa, and one or two are said to be Japanese. Cyclonassa, another sub- 

 genus, agrees with the typical Nassa as regards the soft parts, but is characterized 

 by a very aberrant form of shell. This is smooth, flattened, somewhat like a 

 Nerita, and has an oblique distorted look about the aperture. C. neritcea is a very 

 common Mediterranean shell; two other species being known, one also Medi- 

 terranean, the other from the Black Sea. In the genus Bullia the animal is very 

 similar to that of Nassa, but the foot is larger, and the eyes are wanting. The 

 shells are mostly smooth, and the suture between the whorls is generally filled up 

 with a deposit of callus. The south of Africa may be regarded as the metropolis of 

 this genus, but a few species also occur on the west and east coast, and in Mauritius, 

 Madagascar, and Patagonia. 



The dove shells or Columbellidce are likewise a very numerous family as re- 

 gards species, upward of three hundred having been described. The animal is 

 similar to that of the Buccinidce^ but the central tooth of the radula is not armed 

 with cusps, and the laterals are of a peculiar type. The shells are all small, some 

 quite minute, and offer considerable variation in form and sculpture. Most of the 

 species are prettily colored, and many occur in enormous numbers, and are employed 

 in the manufacture of shell boxes and other ornaments. Columbella abounds in the 

 Tropics, but many are found in temperate latitudes all over the world, and two spe- 

 cies belong to the British fauna. All are carnivorous and mostly littoral, but some 

 affect depths of five or six hundred fathoms. 



The extensive family of the Muricidce contains some of the handsomest and 

 most striking forms of all the Rhachiglossa. The animals have a moderate-sized foot, 

 squarish in front and somewhat pointed behind; the tentacles are slender and 

 pointed, supporting the eyes on the outer margin. The siphon is long, and the re- 

 tractile proboscis, containing the radula, is well developed. The latter is long and 

 narrow, with three rows of teeth; the central tooth having three principal cusps or 

 spines, and other secondary denticles, and the laterals being simple. The horny 

 operculum is variable, having either a lateral or a terminal nucleus. The shells 

 exhibit much diversity of form in the different groups. Murices are carnivorous, 

 feeding upon other mollusks, both gastropods and bivalves. In the typical genus 

 Murex the animal, as it increases in size, produces at intervals beautiful foliations 

 or spine-bearing ridges, nearly always three or more on a whorl, which are some- 

 times continuous up the spire; the siphonal canal being sometimes remarkably long 

 and slender, almost closed and nearly straight. In this group many of the species 



