294 BULLETIN 93, UNITED STATES NATIONAL MUSEUM. 



The Chthamali are exclusively littoral barnacles, many of them 

 living higher up the beach than most Balani. They rarely, if ever, 

 live below low tide. They are usually attached to stones, other bar- 

 nacles, and molluscan shells, but I have seen one species on rushes, 

 evidently from some inside bay or passage. Sometimes they occur 

 on other barnacles attached to floating objects. The walls and valves 

 are particularly subject to corrosion, owing partly to their exposure 

 to the buffets of the surf, partly to the unusually large amount of 

 animal matter they contain chitinous films and pores occupied by 

 filaments from the mantle. This corrosion obscures the external char- 

 acters so much that scarcely any sample can be identified without a 

 deliberate examination of the opercular valves. Even these are sub- 

 ject to great alterations in outline, the effect of erosion of their outer 

 layers. In corroded individuals the sutures of the opercular plates 

 form a figure the shape of the Greek letter 1 F. 



The valves and compartments of alcoholic or fresh specimens may 

 -be isolated and cleaned under the dissecting microscope, but dry sam- 

 ples must be boiled or soaked in caustic potash to free them of the 

 adherent tissues. After that I have found it convenient to mount 

 the opercular valves with glue or mucilage on slips of black card, 

 so that they may be examined under the microscope without risk of 

 loss nearly all of them being diminutive objects of only a few milli- 

 meters' extent. 



Taking the characters of the mouth parts and cirri into account, 

 and making due allowance for distortion and corrosion, and the fre- 

 quent tendency to become cylindric, the species are not very hard to 

 determine, after one becomes accustomed to Chthamali, except in the 

 group of forms typified by C. stcllatus, and widely spread in the 

 Atlantic and communicating seas, and in the oriental seas. I believe 

 that the definition and full illustration of a number of subspecies 

 will materially simplify the study of this group, and a partial revi- 

 sion has been attempted. A very large amount of oriental material 

 must still be collected and overhauled before we can claim to have a 

 fairly complete knowledge of the tropical Indo-Pacific species. 



Thanks to their paltry and insignificant appearance, Chthamali 

 are apt to be overlooked, and our collections would be much poorer 

 than they are were it not that they may often be found on the larger 

 barnacles and shells in museums. 



The supposed difficulty of the genus has probably deterred natural- 

 ists from undertaking serious study of the group. Only one recent 

 species has been described in more than 60 years since Darwin's 

 monograph appeared. 



I have not seen C. dentatus Krauss (South Africa), or C. stellatus 

 var. depressa Poli (Mediterranean, etc.). C. antennatus Darwin is 

 in the collection of the Academy of Natural Sciences from Richmond, 



