THE SESSILE BARNACLES. 



13 



The new classification of sessile barnacles proposed by Professor 

 Gruvel, 1 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 Ohelonibia should logically 

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

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

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

 being constituted as follows, counting from the carina. 



Balanus. 



1. Carina. 



2, 3. Carinolatera. 



4, 5. Latera. 



6. Rostrolatera+rostrum. 2 



Chthamalus. 



1. CarLna, carinolatera wanting. 



2, 3. Latera. 



4, 5. Rostrolatera. 



6. Rostrum. 



The numerical agreement upon which Professor Gruvel's family is 

 based is, therefore, due to the incident that members 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 rostrolatcra, while in CTitliamalus the rostrolatera 

 remain as large, independent compartments, but the elimination of 

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

 time, the characters of the labrum, mandibles, and cirri show that 

 the relationship between the genera is not close, wholly confirming 

 the conclusion drawn from the homologies of the wall plates. 



The family Tetrarneridse Gruvel is heterogeneous by including 

 CJiamsesiplw. This genus has a simple rostrum with ala3, as in 

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

 in Balanus, with which 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 Asymmetrica, is unsatisfactory for the 

 reason that the two divisions or tribes are not directly related. The 

 Asymmetrica (Verrucidae) and the Symmetrica (Balanidse, Chthama- 

 lidse) are two entirely independent derivatives from the pedunculate 

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



Thoracica: 



Suborder TURRILEPADOMORPHA. 



The elongated body is not differentiated into capitulum and peduncle and is cov- 

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

 Families: LEPIDOCOLEHXE, TURRILEPADID.E. 



1 Monographic des Cirrhipecles ou Thecostraces, 1905, pp. 8, 9, Paris. 



2 The rostrum in Salami* is morphologically the rostrum concrescent with the rostrolateral compart- 

 ments, but it is not so in Chthamalus. Professor Gruvel's diagrams, Monographic, p. 194, are inaccurate 

 as to the homclogies of the compartments. 



