96 SKULL OF A 43-MM. HUMAN FETUS. 



(c) Parts showing a difference in No. 886 as compared with la. 



1. Styloid process. It is attached by cartilage to the otic capsule in No. 886, and is 



separate in la. 



2. Mastoid process. It is a free nodule in No. 886 and was attached to the otic capsule 



by cartilage in la. 



3. Paracthmoidal cartilage. It is attached to the ectethmoid by cartilage in No. 886 



and is separated by membrane in la. It is very rudimentary on the right side. 



4. Process of the middle meatus. This may represent the uncinate process. It is alto- 



gether precartilaginous in No. 886 and is long and slender. In la it is a nodule 

 of very young cartilage with a pedicle of precartilage attaching it to the ectethmoid. 



5. Paranasal process. It was a separate cartilaginous nodule in la. 



6. Ala hypochiasmatica. Less developed in No. 886 than in la. 



7. Prechiasmatic commissures. In No. 886 they are of precartilage and are very slender; 



in 7a they are cartilaginous and much stouter. 



8. Prechiasmatic foramina. They are relatively larger in No. 886 than in 7a. They 



were found in the skull of a young human adult. 



(d) Parts found in No. 886 and not described in la. 



1. Cupular process. In No. 886 it is long, slender, and of precartilage. It partially 



encircles the epithelial plug in the anterior naris. Only a short projection of cartilage 

 was described in 7a. This process develops into the medial crus of the greater alar 

 cartilage (Peter, 1913). It is of interest that the process is so fully developed in 

 precartilage at this stage. 



2. Processus ascendens is represented by a spheroidal nodule attached to the upper border 



of the supraoccipital cartilage in No. 886. The corresponding region of 7a is miss- 

 ing. 



3. Processus descendens is plainly marked in No. 886 and is not distinct in la. 



4. Posterior petrosal process is represented in both skulls. 



5. Anterior intraperilymphatic process. It is a very small projection. 



II. ADDITIONAL CARTILAGES. 



1. Parasphenoidal cartilage, or hamular process, is present and intimately- 

 associated with the medial, pterygoid plate. 



2. Branchial-arch skeleton. The following cartilages have been described: 

 Meckel's and Reichert's, with ossicle fundaments; hyoid; thyroid; arytenoid; 

 cricoid; upper tracheal. 



3. Cervical vertebra?. They show arch tips widely separated; those of the 

 atlas are the same distance apart as those of the occipital vertebra. 



4. Paraseptal cartilages and ventrolateral processes are rudimentary in com- 

 parison with those of la. 



III. MEMBRANE BONES. 



All of the membrane bones, with the exception of the nasal, are represented. 

 Some of them are very small, as the medial pterygoid plate, the parietal, and particu- 

 larly the interparietal, lacrimal, tympanic, and goniale. The palatine surface of 

 the maxilla shows a groove indicating the line of earlier complete separation of 

 the maxillary and premaxillary elements. 



IV. NON-SKELETAL PARTS. 



The following structures which are intimately related to the developing skull 

 have been figured and described : 



1. Notochord. It follows a typical course and perforates the anterior end of 

 the preossification center for the basioccipital. 



