2 



MONOGRAPH OF THE ATLANTIDAE. 



exclusively, in the Indian Ocean and the Red Sea. The 

 study of this material has been a most laborious task, as 

 I had to search for the small Atlantidae among innumerable 

 quantities of Copepods, Ostracods, Cumacea, etc., with which 

 each of the glass vessels was crowded. The collection, 

 originating from the surface of the Ocean, is rich in young 

 forms aud in not full-grown specimens, which seems to 

 point to the fact, quite as in the Pteropoda, that the 

 adult specimens of the Atlantidae, and probably of all the 

 Heteropoda, are comparatively rarely found at the surface, 

 and generally prefer deeper zones. 



I should not have been able to bring my study to a 

 rather satisfactory end, if Prof. L. Joubin had not most 

 kindly sent to me, on my request, the valuable types of 

 Souleyet, which are deposited in the » Muséum d'Histoire 

 naturelle" at Paris. I beg this gentleman to take my 

 sincere thanks for the great service he has rendered me. 

 Taking into account its long preservation, for seventy 

 years, in alcohol, the collection proved to be in an excellent 

 state. Unfortunately, two of Souleyet's species, Atlanta 

 quoyana and Atlanta involuta, were not represented, while 

 a third (Atlanta dépressa) had its shell quite dissolved. So, 

 there remains some uncertainty, in my opinion at least, 

 about the two firstnamed forms (which are neither in the 

 British Museum) ; on the other hand, I have been fortunate 

 enough to recognize Atlanta depressa in the collection of 

 Mr. Buitendijk. 



I have thought it useful to figure all the species of 

 Souleyet again 1 j, with exception of those, of which good 

 drawings, leaving no doubt as to the identification of the 

 species, already exist. Souleyet's figures, though generally 

 remarkably accurate, are, however, too small, and he has 

 overlooked several remarkable features about sculpture, 

 which may supply excellent specific characters. 



1) When nothing else is noticed, the figures here given are drawn after 

 Souleyet's types, with the camera. 



Notes from, the Leyden Museum, Vol. XXX. 



