THE BURROWING BARNACLES (CIRRIPEDIA: ACROTHORACICA ) 73 



Dredged at the following points by USDI Bureau of Commercial Fisheries — 

 Pa?cagoula Fishery Station, courtesy of Harvey R. BuUis, Jr., Murex pamum 

 07°58'N 58°23'W 10-11 fathoms; Cymaiium varthenopeum 08°06'N 58°20'W 

 23-26 fathoms; Murex fulvescens 31°19'N 80°33'W, 14.5-15.5 fathoms. 



Dredged in many old shell shards oflf Cape Haze Marine Station, Sarasota, Florida, 

 on "Rhinchodon," with Thomas Hopkins. 



Dredged in Bogue Sound, Morehead City, N.C., in many old shell shards; courtesy 

 of C. G. Bookhout and Lawrence McClosky of Duke University Marine 

 Station. 



Other material found in Murex microphyllus Lamarck from Tul6ar, Madagascar 

 (courtesy of the Institut Royal des Sciences Naturelles de Belgique), is 

 regarded as being identical. 



Type-material: Holotype: USNM 113221. Additional material: 

 Aust, BPB, Brit, Belg, BA, CA, Dublin, Mex, Paris, Seto, UCT, 

 Vict. 



Size (average of four specimens): 3.33 X 1.95 mm. 



The following description is based on material from Puerto Rico 

 coral. 



The operculum is armed with three rows of teeth, some of which 

 are bifid and some rosette shaped. The operculum terminates ventrally 

 (carinally) in a pair of peaks somewhat short of the ventral apertural 

 opening. 



The mantle has a reddish band around the aperture, which is com- 

 mon in this order. The two layers of muscle bands arranged more or 

 less perpendicular and parallel to the mantle aperture are also typical 

 for the order. Very small teeth, bifid or single curved spines, stud the 

 external surface of the mantle evenly except for a slight increase in 

 size and number in a patch near the middle of each side. This patch 

 does not seem to be associated with the lateral bar, as it does in 

 Cryptophialus (fig. 15a). 



A horny disk for attachment to the shell is a conspicuous feature 

 of the dorsal mantle. Males are found clinging to this disk, which is 

 composed of cemented exuviae. 



An orificial knob, bearing short hairs and single teeth curving 

 anteroventrally is prominent at the dorsal end of the mantle aperture 

 or orifice. 



The mantle aperture is heavily armed and ornamented in a char- 

 acteristic manner. The opercular plates fuse to each other and to a 

 heavy supportive bar which extends dorsally and posteriorly toward 

 the attachment disk. These plates terminate about four-fifths of the 

 distance toward the ventral end of the aperture, with the remaining 

 distance filled with light mantle tissue with a few weak teeth and the 

 fringed comb collar which is typical of the order. The plates are pointed 

 into prow-shaped projections pointing ventrally, but no large hooks or 

 articulated spines are present. Studding the apertural plates are num- 



