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Show 1004 MESSRS. B. C. A. WINDLE AND F. G. PARSONS ON [Dec. 19, Gastrocnemius.-This muscle, amongst the Edentata, has, with certain exceptions, the typical mammalian arrangement. In the Bradypodidce the two heads do not unite until they reach the cal-caneum, but they are not twisted in such a way that the inner becomes superficial and then external (cf. Journal of Anat. & Phys. vol. xxviii. p. 414). This is true of Bradypus (1, 2) and Cholcepus (8, 9, 10). In the Manidce (29, 32, 33) the external head is very large and rises a long way up the shaft of the femur-a condition far exceeding anything which we have hitherto observed in any other mammal. It is interesting to notice that nearly all observers have recorded the absence of fabellae except in the Orycteropodidce. Soleus.-Among the Bradypodidce the soleus often rises quite low down on the fibula in Bradypus, in which animal it arose in one case (5) from the middle, and in another (1) from the low*er third of the bone. It is inserted into the calcaneum without joining the tendo Achillis (1, 2). In Cholcepus the chief insertion is also into the calcaneum in front of the tendo Achillis, but Humphry noticed that some of its fibres were continuous with those of the accessorius. Among the Myrmecophagidce its origin was chiefly from the fascia over the deep flexor muscles in Myrmecophaga (11) *. In the last-mentioned animal, in Tamand,ua (14), and in Cyclothurus (19, 20) it is inserted as in the Bradypodidce. In the Dasypodidce it seems usually to join the outer head of the gastrocnemius, but our information is not very clear upon this point. In the Manidce (29, 32) and Orycteropodidce (35, 36) its insertion is as in the Bradypodidce and Myrmecophagidce. It will thus be seen that the Edentata as an order are characterized by the separate insertion of the soleus and the absence or incompleteness of the tendo Achillis. Plantaris.-This muscle is liable to a good deal of variation in the Edentata, and is likely to be confused, on the one hand, with the femoral head of the flexor cruris lateralis (biceps), and, on the other, with the flexor tibialis and fibularis. In the Bradypodidce the muscle was absent in one specimen (1), but in three others (2, 4, 5) it was present as a very large muscle which rose from above the external condyle of the femur, and was inserted into the Ion*1* flexor tendons in the sole of the foot. It is described by some writers as an extra head of the long flexors of the toes. In Cholcepus (8, 9, 10) the muscle is absent, but the condition in this form will be again referred to under the head of the tibialis posticus. Among the Myrmecophagidce it is present in Myrmecophaga (11) and has the usual mammalian insertion into the plantar fascia. In Cyclothurus (17, 19, 20) it is also present, and is inserted into tbe elongated ossicle on the tibial side of the foot. This insertion is interesting when compared with that which is found in the hand of Pedetes (cf. Proc. Zool. Soc. 1898, p. 867), in which the palmaris longus, the serial homologue of the plantaris, is inserted into the 1 In (12) it had the generalized mammalian origin from the back of the head of the fibula. |