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ment resemble those seen in the scale of Thynnus vulgaris, 

 (Cuvier,) which has always been known and described as 

 bone. 



He called particular attention at this meeting to an observation 

 which he had made upon the scales of Megalops, a fish from the 

 Gulf of Mexico, and commonly classed in the order Chipea^ In 

 this fish the upper or ornamental layers of the scale contain lacu- 

 nae which correspond exactly, in form and arrangement, with 

 those of the ganoid scales of Lepidosteus. A further resem- 

 blance to ganoid scales is seen in the fact, that the concentric 

 ridges which mark the upper surface of the scale of Megalops, 

 are armed with tooth-like projections of the hardness of tooth 

 enamel. 



Prof. Agassiz said that he attached considerable importance to 

 this unexpected point of resembhmce between Megalops and the 

 ganoid fishes. He had been inclined, upon other grounds, to con- 

 sider Megalops to be nearly allied to the class of ganoids, as is 

 generally supposed. 



The President gave the result of some examinations 

 of a large number of fcetal pigs. 



He thought that zoologists had not given sufficient importance 

 to the very slight connection between the foetus and the parent. 

 Strictly speaking there was no placenta — the vessels of the foetus 

 and the parent being brought in relation only by means of very 

 minute diffused villi and slight foldings of the chorion. These 

 conditions are intermediate between those of the marsupials and 

 the ruminants, and make the transition so gradual, that the sepa- 

 ration of the Mammalia into two sub-classes, viz : the Placentals 

 and Iraplacentals, is not well defined. 



He had also found in one litter three foetuses in which the 

 brain protruded through the collapsed cranial walls, and was 

 represented by a very small and imperfectly developed mass of 

 cerebral matter. This would probably have resulted in what is 

 called the anencephalous condition. In addition to the above mal- 

 formations, he had met with one monstrosity, consisting of a single 

 head, with a small opening on the occiput, and having two sets 

 of upper extremities ; the lower part of the body was double 

 from the lumbar region. The livers of the two formed a hernia 



