226 REPORT OF NATIONAL MUSEUM, 1901. 



Following the crinoids were shown the fossil cephalopoda, with 

 special reference to the ammonites. Here the testaceous anatomy is 

 not so complicated as in the crinoids and requires fewer descriptive 

 labels in the introductory series. 



INTRODUCTORY LABELt 

 CLASS CBtHALOPODA. 

 The pearly nautilus, squid, and cuttlefish are three types of h\nng Cephalopods 

 Jete an"! are resected to marine waten, and are the mos tl ^3™* 

 elaL of the Mollusca, a division of the animal kingdom including besides the Ceph- 

 thebivalve (dams, oysters), and univalve (drills snails) shells. 

 The onus here shown are those having external chambered shells They 

 .,,„,, Z Paleozoic and Mesozoic seas. In the Tertiary seas the shelled ^Ceph- 

 ;;;;, 1,,^, to a few forms very much ^*^*£%£^« 

 the Pacific « »«van (See complete animal m jar, with alcohol ) 11 she In u be 

 straight curved, or roiled, and is divided at regular interval! by septa. The cham 

 bers thus formed are connected with the animal by a tube or mpho. 



Th" sheled Cephalopods are divided into two orders, NauUloidea and Ammonia 

 Intti former the . u*L (Hues of junction of the , 7 „ with the outer shell) are 

 usually slight or merely undulated, while in the latter they are mure or le» 

 abundantly lobed and inflected, the greatest complexity having been attained 

 during MeLoic time. Of Nautiloids about 2,500 species are known, and of Arnmo- 

 n ^ iiol^han 5,000. The latter died out during Mesozoic time o-^aigh 

 Nautiloidea grew to a length of more than 15 feet, while certain coiled Ammonoida 

 have attained a diameter of 5 feet. , 



The classification here adopted is that of Hyatt, as published in Text Look of 

 Paleontology, by Zittel and Eastman. 



SPECIAL EXPLANATORY LABEL. 

 NVUTII/l S POMPILIUS UNX.Kl'S. 

 (Shell with animal. 1 

 :T;,T^,.^ t, pertu, the she.] when the animal U withdraw, 



, llill ,„ i | > ,•;,„„ „-,,,,,, i, is then violently expelled, the reaction driving th. creature 



backward. 



(() Tentacles, of which there are about ninety. 



SEPTA AND SIPHO. 



Nautilus macromphalus Sowerby. 

 New Caledonian sea. .,, ., 



Theanimal is removed and the shell sectioned to show the various parts, with 

 technical names applied directly to each part. 



JAWS OF V NAUTILOrD. 



Temnocheilus bidorsatus Schlotheim. 

 (Conchorhynchus avirostris.) 

 triassic 1 muschelkalk). 

 Wurzburg, Bavaria, Germany. 29104. 



