355 



MISCELLANEOUS. 



On the Occurrence of Cucumaria digitata in the Firth of Forth, 

 By Robert O. Cunningham, M.D., Prestonpans. 



As the gigantic Sea-Cucumber {Cucumaria digitata) must be 

 regarded as one of the rarer Echinodermata of the Firth of Forth, 

 I may mention that I obtained a fine specimen of it in the sum- 

 mer of 1863. It measured upwards of a foot long, was of a fine 

 mottled purple colour, and lived for a considerable time in a state of 

 captivity. 



On the Milk-dentition of the Walrus. By Professor Peters. 



Malmgren has stated that Wiegmann*s formula for the milk- 

 dentition of the Walrus, namely, f j- f ^ f , is incorrect, and that the 

 true formula is | ^f ^f . He indicates that Wiegmann's notion was 

 founded upon a single case in which the presence of an alveolus 

 already filled up led to the supposition that there was a fifth upper 

 molar ; but states that, after an examination of many skulls of the 

 Walrus of various ages, he has never found any trace of this fifth 

 molar. If, therefore, a fifth molar should occur in the great gap 

 between the third upper molar and the fourth milk-molar , this must 

 be regarded as an abnormal case. 



The Berlin Museum has received the skull of a young Walrus 

 apparently about a year and a half old, which, besides the perma- 

 nent teeth, "I Y ^ ~ |, still exhibits in the lower jaw the two outer 

 milk-incisors, and in the upper jaw, on the right side, the fourth and 

 fifth, and on the left side the fourth and the shallow alveolus of the 

 fifth milk-molars. The position of these teeth is so regular on each 

 side, not between the fourth milk-molar and the third permanent 

 molary hut further back, and nearly on the same transverse line with 

 the hinder margin of the maxillary zygomatic process, that they can- 

 not well be regarded as abnormal structures, and therefore furnish 

 new evidence of the correctness of Wiegmann's formula. 



The knowledge of the milk-dentition of this animal is of the more 

 consequence, because it is only by it that we can explain the super- 

 numerary teeth in the moutli of the mature animal, which are to be 

 regarded as abnormally late-developed milk-teeth. Amongst these, 

 in the author's opinion, are to be reckoned not only a large fourth 

 molar in the lower jaw, which occurs in two half-grown animals and 

 one mature one, and, singularly enough, only on the left side in all 

 three, but also an anomalous second incisor on the right side of the 

 upper jaw, which has the form of a mushroom, and occurs in a skull 

 having tusks more than half a metre in length. Wiegmann also 

 cites an observation of Fremery's upon the occurrence of five true 

 upper molars, of which the two hindermost were very small, as a con- 

 firmation of his view. 



With regard to the systematic position of the Walrus, it cannot 

 be denied that the affinity between the Lutrina and Pinnipedia^ 

 indicated upon osteological grounds by Steenstrup and Sundevall, 



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