488 Miss Agnes Crane — Recent and Fossil Cephalopoda. 



ference of 16 inches at their vinion to the body. A new genus of 

 calamaiy, allied to the Architeuthis of Steenstrup, with arms measur- 

 ing over 23 feet, was discovered on the island of St. Paul, in the 

 Indian Ocean, by M. Charles Velain, the naturalist attached to the 

 French Expedition for the observation of the transit of Venus, at that 

 station.^ The size attained by some of the fossil species will be 

 noted in the sequel. 



The Cephalopoda^ are more highly organized than any other mem- 

 bers of the sub-kingdom Mollusca ; and, consequently, rank at the 

 summit of that great natural division of the animal kingdom, com- 

 prising the invertebrated animals. The technical name of this impor- 

 tant group of molluscs describes the position of their locomotive and 

 prehensile organs, which are attached in a circle round the mouth. 

 The brain, eyes, heart, and lungs, are well developed. The Cephalopods 

 are all inhabitants of the sea, and are almost universally distributed 

 in the existing oceans. The geological range of the class is also 

 great, for they occur, more or less abundantly, in a fossil state in all 

 the marine deposits, ranging from the Upper Cambrian formation 

 npwai-ds throughout the whole sequence of geological strata. They 

 are divided into twb groups, a classification (first proposed by Prof. 

 Owen)^ based on the respiratory system. The more lowly organized 

 tetrabranchiate, or four-gilled, Cephalopods are characterized by the 

 possession of a many-chambered external shell, and the absence of 

 an ink-bag. Our knowledge of the anatomy of this once dominant 

 class, so abundantly represented in the seas of the Palaeozoic and 

 Secondary periods, is founded solely on the structure of the Pearly 

 Nautilus, the only member of the order surviving in the existing 

 oceans. Dead shells of this genus, of which there are at most three 

 species, are a common object in our museums, but the animal in- 

 habiting that wondrous dwelling has but rarely been obtained. It 

 was, however, certainly known to Aristotle, but no further observa- 

 tions were recorded until those of the Dutch naturalist Eumphius 

 in 1705. It long headed the list of rarities desired by Cuvier, but 

 that illustrious naturalist unfortunately died three days before the 

 publication, in 1832, of Professor Owen's elaborate memoir* based 

 on the study of a specimen, caught by his former pupil. Dr. Bennett, 

 when drifting on the surface of the South Pacific Ocean, off one of 

 the New Hebrides Islands. A living specimen was also dredged 

 in 300 fathoms during the cruise of the " Challenger," near the 

 Windward Islands.^ The shell of the Nautilus is divided by shelly 

 partitions or septa into many cells or chambers, which are connected 

 by a siphuncle, or tube, centrally situated. The animal inhabits the 

 last and most spacious chamber, and has the power of forming a 

 fresh one when necessary. Each chamber was thus occupied in 



^ Remarques au sujet de la faune des iles Saint Paul et Amsterdam, etc. Charles 

 Velain, Paris, 1878. 8vo. 



^ " Head-footed Mollusca," from Ke(j>a\i] ' head ' and ttovs ' foot.' 



^ See also Baron Cuvier's Anatomie des Mollusques for details of the structui'e 

 of the Dibranchiata. 



* On the Pearly Nautilus. Eiohard Owen. Loiidon, 1832. 4to. 



5 Proceedings Eoyal Society, 1874. 



