110 REPORT — 1855. 



"The 'centra ' of the thirty-fourth and thirty-fifth divisions of the spinal series 

 are ossified together. A single piece indicates the union of the bodies of the thirty- 

 sixth, thirty-seventh, thirty-eighth, and thirty-ninth vertebrae, the spinous transverse 

 processes pointing obliquely backward. The fortieth and forty- first vertebral bodies 

 are united. The forty-second is independent. The forty-third and fort}--fourth have 

 coalesced. In these latter five instances, the supra and infra axial developments have 

 recovered much of their natural character. 



" The twelve remaining segments of the spinal series, from the forty-fifth to the 

 fifty-sixth inclusive, alone present a completely liealthy aspect, and a glance at their 

 uniform disposition affords a criterion of the extreme mal-arrangement to which the 

 abdominal vertebrae have been subjected." 



On the Species o^Meriones and Arvicolae found in Nova Scotia. 

 By J. W. Dawson. 



There appear to be two species of Meriones in Nova Scotia : one of them is 

 identical with M. Lahradoriiis of Sir J. Richardson, diftering only in some trifling 

 characters ; the second species is smaller, darker coloured, and has coarser hair. 

 The average dimensions of three adult specimens are, — length of head and body, 3 

 inches 6 lines ; tail, 4 inches 8 lines ; tarsus and foot, 1 inch 4 lines. The author 

 had not found any description of this last species ; but would not desire to name it 

 as a new species until he had made further inquiry. Should it prove to be new, 

 he would claim for it the name M. Acadicus. This species inhabits grain fields. 

 It does not burrow, but prepares forms in sheltered places, lying very close ; and, 

 when disturbed, escaping by a few rapid leaps or bounds. It feeds by day, and does 

 not appear to prepare any store of food for winter. It is usually stated that these 

 elaping mice are adapted to level and open countries ; it therefore appears singular 

 that in a country originally densely wooded two species should exist. Their natural 

 habitat may have been those places from which the woods have been removed by 

 fire, and replaced by herbaceous plants and shrubs. The most common Arvicola in 

 Nova Scotia is the A. Fennsylvanica, which in form and habits closely resembles the 

 European A. vulgaris. It burrows, forming a neat nest, having two entrances each 

 with a sort of antechamber to enable the animal to turn itself. It excavates 

 galleries under the snow in winter, devouring grass-roots, bark of trees, &c. ; and at 

 the same season it often resorts to barns and outhouses. Some other specimens of 

 Arvicola vf ere exhibited, closely approaching in their characters to the A. Novohora- 

 censis. The white-footed mouse, Mus leucoptis, also occurs in Nova Scotia, and the 

 domestic mouse and brown rat have been introduced and naturalized, while of the 

 black rat only a few specimens have been found in the city of Halifax. It was 

 stated that some of the specimens exhibited had been collected by Mr. Winton and 

 Mr. Downes of Halifax. 



Notes on the Homologies of Lepismidce. By Professor Dickie, M.D. 



The species on which the present remarks are founded is Machilis maritima, an 

 insect which is common on different parts of our shores, lurking under stones and 

 in crevices of rocks near high-water mark. It is destitute of wings, but provided 

 with means of locomotion for running and leaping. The thoracic and abdominal 

 zoonites present considerable uniformity in size ; the former have the usual number 

 (viz. three pairs) of well-developed limbs ; the abdominal zoonites are eleven in 

 number, and each, with the exception of the penultimate and the last, is provided 

 with a pair of rudimentary limbs. The existence of these appendages, their resem- 

 blance to those attached to the base of the second and third pairs of thoracic limbs, 

 and their relations to the elements of the zoonites with which they are connected, 

 enable us to trace with facility the true homology of the parts of the ovipositor in 

 Machilis. 



In a series of very elaborate papers lately published in the ' Annales des Sciences 

 Naturelles,' Lacaze-Duthiers has arrived at the conclusion that there is unity of 

 composition in the structure of stings and ovipositors in different orders of the class 

 of insects. From examination of a single species, viz. Lepisma saccharina, he con- 

 cludes thar in the Thysanoura, as in other orders, the ninth urite forms the ovi- 



