132 APORRHAIS. 



cording to Mr. Couch, Solaster papposus also reckons it an 

 agreeable kind of food ; when the soft portion has been digested, 

 the empty shell is rejected, and becomes the habitation of a 

 Sipunculus, which narrows the too capacious entrance with 

 agglutinated sand. Specimens from deep water are smaller than 

 those from the coast. The top of old but living shells which 

 had lost their upper story, is sometimes closed by a semispiral 

 plug or septum of new shelly matter ; the apex is very seldom 

 perfect in full-grown specimens. When the outer lip is complete 

 the subsequent growth takes place by adding fresh layers inside, 

 so that the age of the individual is probably shown by the 

 number of such layers. In immature specimens the commence- 

 ment of the pterygoid or wing-like flap of the outer lip is defined 

 by a bit of enamel along the mouth, which likewise lines the 

 canal at the base as well as the upper process of the flap. Still 

 younger specimens, before any sign of the flap appears, have the 

 outer lip flexuous, with a wide and deep sinus at the upper part, 

 and a long straight canal at the base. In this stage of growth 

 they strongly resemble Fusi. The fry form a short cylinder. 

 Monstrosities are not uncommon, especially in the shape and 

 relative size of the digitated processes ; the basal point, however, 

 is always formed like a spear-head." 



According to Morch Chiropteron semilunare of Sars is prob- 

 ably the larval stage of Aporrhais. 



A. SERRESIANUS, Michaud. PI. 12, fig. 32. 



Whitish, or light yellowish brown. Differs from the preceding 

 species by its long posterior and anterior canals, and by the 

 outer lip being three-spined. Length, 2 inches. 



Europe, from Norway to the Mediterranean Sea. 



Perhaps more generally known under the name of A. pes- 

 carbonis, Brong., which is, however, a wrong identification, the 

 latter being a fossil and different species. Dr. Gwyn Jeffreys 

 gave it the name of A. Macandreoe. 



A. SENEGALENSIS, Gray. (Un figured'.) Senegal. 



The (insufficient) description indicates close affinity or identity 

 with A. 



