iv ACROTHORACICA ASCOTHORACICA 93 



distinguished from all the foregoing Cirripedes by the presence 

 of a well -developed abdomen. Since the discovery of other 

 allied genera, it has been decided that the abdomen is equally 

 reduced in these forms, and that the terminal appendages do not 

 belong to this region, but to the thorax. 



The sexes are separate. The body of the female (Fig. 64, A) 

 is enclosed in a chitinous mantle, armed with teeth by which 

 the excavation is effected, and is attached to the cavity in the 

 host by means of a horny disc. Upon this disc the dwarf 

 males (B) are found. 



Alcippe larnpas inhabits holes on the inner surface of dead 

 FIIXKS and Buccinum shells ; Cryptophialus minutus the shells 

 of Concholepas peruviana ; C. striatus l the plates of Chiton ; 

 Kochlorine hamata the shells of Haliotis ; and Lithoglyptes 

 varians shells and corals from the Indian Ocean. 



Sub-Order 4. Ascothoracica. 



These are small hermaphrodite animals completely enveloped 

 in a soft mantle, which live attached to and partly buried in 

 various organisms, such as the branching Black Corals (Gerardia). 

 They retain the thoracic appendages in a modified state, and the 

 body is segmented into a number of somites, the last of which 

 probably represents an abdomen. 



Laura gerardiae, described by Lacaze Duthiers, 2 is parasitic 

 on the stem of the "Black Coral," Gerardia (vol. i. p. 406); it 

 has the shape of a broad bean, the body being entirely enclosed in 

 a soft mantle, with the orifice in the position corresponding to 

 the hilurn of a bean. The body lying in the mantle is composed 

 of eleven segments, and is curved into an S-shape. Its internal 

 anatomy is entirely on the plan of an ordinary Cirripede. 



Petrarca bathyactidis, G. H. Fowler, 3 was found in the 

 mesenteric chambers of the coral Bathyactis, dredged by the 

 Challenger from 4000 metres. The body is nearly spherical, 

 and the mantle-opening forms a long slit on the ventral surface. 

 The mantle is soft, but is furnished on the ventral surface with 

 short spines. 



The antennae, which form the organs of fixation, remain 



1 Beriidt, Sitzb. Ges. Naturfr. Berlin, 1903, p. 436. 



2 Arch. Zool. Exp. viii., 1880, p. f>37 '. 

 3 Quart. J. Mia: Sci. xxx., 1890, p. 107. 



