ARREST OF DEVELOPMENT. 51 



197. The anterior portion of the brain of the same, showing the 



entire absence of the corpus callosum and fornix. The 

 remainder of the brain had decomposed before it was re- 

 moved from the cranial cavity. Hunterian. 



198. The head of a fcetal Lamb with the eyes fused into a single 



median globe, the whole ethmoid region being absent. 

 The maxillae are large, and are placed at right angles to 

 the cranial axis. All the internal parts have been re- 

 moved, so that no accurate description can be given. 



Hunterian. 



199. A vertical longitudinal section of the head and neck of a 



foetal Lamb, with deficiency of the facial axis and pre- 



sphenoid, and complete fusion of the eyes. The brain is 



very defective in front. 



The maxillae are at right angles to the cranial axis ; they form 

 large cancellous masses of bone, which are fused together in the 

 mesial line. There is no vestige of a mandible. The ears are 

 fused together, so that there is a single auditory meatus commu- 

 nicating with the pharynx by a spiracle. The other characters 

 are precisely similar to those seen in synotia generally. 



Presented by Dr. E. L. Ormerod, 1864. 



E. Prostho-epencephalic deficiency. 

 Syn. Stomocephalie, Geoff. 



The defect of the cranio-facial axis commences between the 

 ear-capsules and becomes gradually more marked in front of 

 this region ; the basisphenoid may be partially developed, but 

 the axis is entirely absent anteriorly to it. No arches are de- 

 veloped in front of the hyoid arch. The tympanic cavities and 

 external ears are more or less fused together. The cranial cavity 

 is small and rounded. The face, when present, consists of a 

 frontal proboscis and a pair of more or less united eyes. Some- 

 times the maxillae are represented by a small papilla. These 

 parts are placed immediately beneath the skull. The term cy- 

 clocephalus has been applied to this form. 



In a more highly arrested condition the face presents only a 

 pair of external ears, sometimes fused together in the median 

 line. An atrophied median eye sometimes exists, but is more 

 commonly absent. In such cases the frontal and maxillary pro- 



E2 



