Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_name_67 ( sequence_length__aa_ INTEGER, common_name VARCHAR, divergence_from_human_lineage__mya_ VARCHAR )

### Question ###
What is the sequence length (aa) of the protein with the common name Purple Sea Urchin and a divergence from human lineage less than 742.9?

### Accurate SQL ###

SELECT SUM(sequence_length__aa_) FROM table_name_67 WHERE common_name = "purple sea urchin" AND divergence_from_human_lineage__mya_ < 742.9