56 



IOWA ACADEMY OF SCIENCES. 



area then shows, thus far, a fauna numbering over 60 per cent of the species known 

 to Iowa. That this list will be largely increased is most probable. 



The nature of the fish fauna of Central Iowa, so far as known, may be best 

 exhibited in the following tabular view: 



ON AN ABNORMAL HYOID BONE IN THE HUMAN SUBJECT. 



BY K. ELLSWORTH CALL. 



( ABSTRACT.) 



The hyoid bone lies at the base of the tongue just above the upper border of 

 the thyroid cartilage. It is not articulated with any other bone in the body. 



It is usually studied as consisting of five parts, all of which may readily be 

 distinguished in the normal specimen, especially in the young subject. There is 

 the body of the bone, or the basi-hyal; there are also two cerato-hyals, or lesser 

 cornua, and two thyro-hyals, or greater cornua. The whole forms a horse-shoe 

 shaped bone to which the name hyoid has been given in allusion to the shape of 

 the Greek letter tipsUon, which the bone greatly resembles. 



In the normal bone the body is commonly compressed antero-posteriorly, curved 

 and extended transversely. On the anterior lower border is a rather prominent but 

 blunt tubercle. Owen describes the cerato-hyals as "mere pisiform nodules of 

 bone projecting from the line of union of the basi-hyal and thyro-hyal portions,'' 

 that is to say, they arise from the area of junction. Strong, somewhat rounded 

 ligaments extend from the cerato-hyals, or lesser cornua, to the styloid processes of 

 the temporal bones, or rather to their petrosal portions, 



Also, normally, both the thyro-hyals and the cerato-hyals are separated from the 

 basi-hyal or body to a late period in life. A slight expansion of the posterior end 

 of the thyro-hyals is usually seen and these often bear — indeed I have never seen 

 any other condition — epiphyses. From these processes extend ligaments which 

 reach to the thyroid cartilage and this occasions the name bestowed upon them. 

 All these five bones become completely ossified and ankylosed at from thirty-five 

 to forty years of age. 



It may be further remarked that the cerato-hyals are described by Holden as 

 being " of the size of barley-corns." 



