THE SESSILE BARNACLES, 



13 



The now classification of sessile barnacles proposed by Professor 

 Gruvel/ cast aside Darwin's principles. The families were based 

 upon the number of compartments in the wall — eight, six, or four. 

 This system seems to me to be retrogressive at every point. His 

 family Octomeridse is a natural group, though Pachylasma forms a 

 complete transition to his Hexameridae, and Ghelombia should logically 

 have been included. His Hexameridas contains genera with six com- 

 partments, but tliey are not the same six in the different genera, as 

 may be seen by a comparison of Balanus and Glitliamalus, the walls 

 being constituted as follows, counting from the carina. 



Balanus. 



1. Cariaa. 

 2, 3. Carinolatera. 

 4, 5. Latera. 



6. Rostrolatora-f-rostrum.^ 



Chihamalus. 



1. Carina, carinolatera wanting 



2, 3. Latera. 



4, 5. Rostrolatera. 



G. Rostrum. 



The numerical agreement upon which Professor Gruvel's family is 

 based is, therefore, due to the incident that meml^ers of two collateral 

 phyletic series have independently reached the hexamerous stage. 

 In Balanus it has been reached by complete concrescence of the 

 rostrum with the rostrolatera, while in Cldhamalus the rostrolatera 

 remain as large, independent compartments, but the elimination of 

 carinolatera brings the number of mural plates down to six. Mean- 

 time, the chai'acters of tlie labrum, mandibles, and cirri show that 

 the relationship between the genera is not close, wholly confirming 

 the conclusion drawn from the homologies of the wail plates. 



The family Tetrameridte Gruvel is heterogeneous by including 

 Clianixsiplio. This genus has a simple rostrum with aire, as in 

 CJitliamalus, while the other genera have the rostrum composite, as 

 in Balanus, with wliich they also agree in the structure of the labrum 

 and cirri. 



The usual classification of sessile barnacles as a suborder Operculata, 



with the tribes Symmetrica and Asymnietrica, is unsatisfactory ("or the 



reason that the two divisions or tribes are not <lirectly relate<l. Tiie 



Asymmetrica (Verrucidffi) and the Symmetrica (Balanidte, Chtliama- 



lidse) are two entirely inde])endent derivatives from the peduiu-ulate 



group. We have, then, the following Suborders of the Order 



Tlioraeica: 



Siiljorcler TURRILEPADOMORPHA. 



The elongated body is not dirferentiatcd into capituliim and jx'duncle and is cov- 

 ered with longitudinal series of large, similar, imbricating plates. Palteozoic. 

 Families: Lepidocoleid.e, Turrilepadid^. 



' Monographic des Cirrhip^des ou Thocostraces, 1905, pp. 8, 9, Paris. 



2 The rostrum in Balanus is morpliolojjieally the rostnim concrescent with the rostrolateral lompart- 

 ments, but it is not so in Chthamalm. Professor Gravel's diagrams, Monoyraphk , \i. I'JI, are inaccurate 

 as to the liomclogies of the compartments. 



