THE BURROWING BARNACLES (CIRRIPEDIA: ACROTHORACICA) 143 



most readily found in heavy-shelled clams and brachiopods until the 

 Mesozoic, when these shells became thinner. They then changed to 

 ammonites and echinoids, and finally to gastropods as these heavy- 

 shelled forms became abvmdant in the Cenozoic. 



It is quite certain that as more is known about the shapes of the 

 burrows of these forms, more species will be described from the fossil 

 record. Sponge and bryozoan burrows are common, and may be 

 recognized by several distinct features. Sponge burrows usually 

 perforate the shell, with small, round holes connecting larger spherical 

 chambers. The burrows are often neither separate and distinct, nor 

 with only a single aperture. Bryozoan colonies, being connected by 

 stolons, usually have a branching pattern visible somewhere in the 

 colony, and the individual burrows are connected by smaller holes 

 formed by the stolons. 



Acrothoracican burrows can be close enough to coalesce. I have 

 found this condition in shells containing specimens of Cryptophialus 

 melampygos , Berndtia purpurea, Trypetesa lampas, or T. lateralis. 

 The usual situation, however, is for the individuals to have distinct, 

 separate burrows, with a single aperture (except T. lateralis, which 

 has the second minute opening of the external mantle flap). They 

 are frequently grouped together, especially around the umbo or beak 

 of a bivalve, where the periostracum has been abraded. The position 

 and orientation of burrows on the shell may indicate swimming 

 habits of such forms as belemnites (Seilacher, 1968). 



Distribution 



As indicated by the map of world distribution (fig. 41), the order 

 Acrothoracia is cosmopolitan. 



The species with the widest known range are Lithoglyptes spinatus 

 and Kochlorine hamata. The former is found scattered through the 

 Pacific Ocean, in the Caribbean, the Indian Ocean, and in the Red 

 Sea. K. hamata is found on the eastern and western Pacific, and the 

 Indian Ocean, and is the only species in the Mediterranean. 



The most restricted distribution seems to be that of Australophialus 

 melampygos, found only in New Zealand. It has a larva which does 

 not swim. 



Other generalities can be drawn as follows: Weltneria is in the 

 Indo-Western Pacific. Lithoglyptes is a complex genus with wide 

 distribution of imperfectly differentiated species. All species should 

 be expected to have appreciable distributions when fully known. 

 Kochlorine is uddely represented by Kochlorine hamata. K. jloridana 

 appears to be in Madagascar (Malagasy Republic) in addition to 



